dizocilpine-maleate and Ischemic-Attack--Transient

Topics: Animals; Benzazepines; Body Temperature; Brain; Brain Injuries; Brain Ischemia; Calcium Channel Blockers; Dextromethorphan; Dizocilpine Maleate; Drug Therapy, Combination; Humans; Ischemic Attack, Transient; N-Methylaspartate

Ischemic damage, chiefly of the focal type, and axonal disruption (diffuse axonal injury) are the major factors causing brain damage after human head injury. About one third of this damage may be delayed hours or days after the injury. Evidence from four animal models, each relevant to different aspects of human head injury, has shown that excitatory amino acid-induced changes are responsible for a proportion of the posttraumatic sequelae and that these effects can be blocked by EAA antagonists. This evidence is reviewed, and the implications for the conduct of human trials with EAA antagonists are discussed.

Topics: Animals; Brain Damage, Chronic; Brain Injuries; Brain Ischemia; Central Nervous System Depressants; Dizocilpine Maleate; Excitatory Amino Acid Antagonists; Humans; Ischemic Attack, Transient; Spinal Cord Injuries

Inflammatory responses have been shown to modulate the pattern and degree of ischemic injury. Previously, we demonstrated that intracorpus callosum microinjection of lipopolysaccharide (LPS, a well-known endotoxin) markedly induced inflammatory responses confined to ipsilateral hemisphere and aggravated cerebral ischemic injury. Here we report that LPS injection increases the degree of N-methyl-d-aspartate (NMDA) receptor-mediated excitotoxicity, one of major causes of cerebral ischemic injury. Intracorpus callosum microinjection of LPS 1 day prior to ischemic insults augmented intraneuronal Ca(2+) rise in rat brains subjected to transient occlusion of middle cerebral artery. Intraperitoneal administration of memantine, a NMDA receptor antagonist, reduced the LPS-enhanced calcium response as well as ischemic tissue damage. Western blot and immunohistochemistry data showed that the level of IL-1β was enhanced in LPS-injected rat brains, particularly in isolectin-B4 immunoreactive cells. Intraventricular microinjection of recombinant rat IL-1β aggravated cerebral ischemic injury, which was significantly reduced by memantine. Intraventricular injection of anti-IL-1β antibody significantly reduced the cerebral infarction aggravated by LPS preinjection. The results indicate that IL-1β released from isolectin-B4 immunoreactive cells enhanced excitotoxicity, consequently aggravating ischemic brain injury.

Topics: Animals; Anti-Inflammatory Agents; Cerebral Infarction; Corpus Callosum; Dizocilpine Maleate; Drug Synergism; Indicators and Reagents; Infarction, Middle Cerebral Artery; Inflammation; Injections, Intraventricular; Interleukin-1beta; Ischemic Attack, Transient; Male; Memantine; Microinjections; Plant Lectins; Rats; Rats, Sprague-Dawley; Receptors, N-Methyl-D-Aspartate

Although recent results suggest that GluR6 serine phosphorylation plays a prominent role in brain ischemia/reperfusion-mediated neuronal injury, little is known about the precise mechanisms regulating GluR6 receptor phosphorylation. Our present study shows that the assembly of the GluR6-PSD95-CaMKII signaling module induced by brain ischemia facilitates the serine phosphorylation of GluR6 and further induces the activation of c-Jun NH2-terminal kinase JNK. More important, a selective CaMKII inhibitor KN-93 suppressed the increase of the GluR6-PSD95-CaMKII signaling module assembly and GluR6 serine phosphorylation as well as JNK activation. Such effects were similar to be observed by NMDA receptor antagonist MK801 and L-type Ca(2+) channel (L-VGCC) blocker Nifedipine. These results demonstrate that NMDA receptors and L-VGCCs depended-CaMKII functionally modulated the phosphorylation of GluR6 via the assembly of GluR6-PSD95-CaMKII signaling module in cerebral ischemia injury.

Topics: Analysis of Variance; Animals; Benzylamines; Calcium-Calmodulin-Dependent Protein Kinase Type 2; Disease Models, Animal; Disks Large Homolog 4 Protein; Dizocilpine Maleate; Excitatory Amino Acid Antagonists; GluK2 Kainate Receptor; Immunoprecipitation; In Situ Nick-End Labeling; Injections, Intraventricular; Intracellular Signaling Peptides and Proteins; Ischemic Attack, Transient; Male; Membrane Proteins; Nifedipine; Phosphorylation; Protein Kinase Inhibitors; Rats; Rats, Sprague-Dawley; Receptors, Kainic Acid; Serine; Signal Transduction; Sulfonamides

Protease-activated receptor 1 (PAR1) is a G-protein coupled receptor that is expressed throughout the central nervous system. PAR1 activation by brain-derived as well as blood-derived proteases has been shown to have variable and complex effects in a variety of animal models of neuronal injury and inflammation. In this study, we have evaluated the effects of PAR1 on lesion volume in wild-type or PAR1-/- C57Bl/6 mice subjected to transient occlusion of the middle cerebral artery or injected with NMDA in the striatum. We found that removal of PAR1 reduced infarct volume following transient focal ischemia to 57% of control. Removal of PAR1 or application of a PAR1 antagonist also reduced the neuronal injury associated with intrastriatal injection of NMDA to 60% of control. To explore whether NMDA receptor potentiation by PAR1 activation contributes to the harmful effects of PAR1, we investigated the effect of NMDA receptor antagonists on the neuroprotective phenotype of PAR1-/- mice. We found that MK801 reduced penumbral but not core neuronal injury in mice subjected to transient middle cerebral artery occlusion or intrastriatal NMDA injection. Lesion volumes in both models were not significantly different between PAR1-/- mice treated with and without MK801. Use of the NMDA receptor antagonist and dissociative anesthetic ketamine also renders NMDA-induced lesion volumes identical in PAR1-/- mice and wild-type mice. These data suggest that the ability of PAR1 activation to potentiate NMDA receptor function may underlie its harmful actions during injury.

Topics: Analysis of Variance; Animals; Brain Injuries; Cells, Cultured; Corpus Striatum; Disease Models, Animal; Dizocilpine Maleate; Embryo, Mammalian; Excitatory Amino Acid Agonists; Excitatory Amino Acid Antagonists; Female; Guanidines; Injections, Intraventricular; Ischemic Attack, Transient; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; N-Methylaspartate; Neurons; Oligopeptides; Pregnancy; Rats; Receptor, PAR-1; Receptors, N-Methyl-D-Aspartate

The c-Jun-N-terminal kinase (JNK) pathway has been shown to play an important role in excitotoxic neuronal death and several studies have demonstrated a neuroprotective effect of D-JNKi, a peptide inhibitor of JNK, in various models of cerebral ischemia. We have now investigated the effect of D-JNKi in a model of transient focal cerebral ischemia (90 min) induced by middle cerebral artery occlusion (MCAo) in adult male rats. D-JNKi (0.1 mg/kg), significantly decreased the volume of infarct, 3 days after cerebral ischemia. Sensorimotor and cognitive deficits were then evaluated over a period of 6 or 10 days after ischemia and infarct volumes were measured after behavioral testing. In behavioral studies, D-JNKi improved the general state of the animals as demonstrated by the attenuation of body weight loss and improvement in neurological score, as compared with animals receiving the vehicle. Moreover, D-JNKi decreased sensorimotor deficits in the adhesive removal test and improved cognitive function in the object recognition test. In contrast, D-JNKi did not significantly affect the infarct volume at day 6 and at day 10. This study shows that D-JNKi can improve functional recovery after transient focal cerebral ischemia in the rat and therefore supports the use of this molecule as a potential therapy for stroke.

Topics: Analysis of Variance; Animals; Behavior, Animal; Cerebral Infarction; Cerebrovascular Circulation; Disease Models, Animal; Dizocilpine Maleate; Enzyme Inhibitors; Functional Laterality; Ischemic Attack, Transient; Male; Neurologic Examination; Neuroprotective Agents; Peptides; Psychomotor Performance; Rats; Rats, Sprague-Dawley; Recognition, Psychology; Recovery of Function

Recombinant tissue plasminogen activator (rt-PA) treatment improves functional outcome after acute ischemic stroke, inducing reperfusion by its thrombolytic activity. Conversely, there is evidence that rt-PA can mediate neuronal damage after ischemic brain injury in vivo. In addition to other mechanisms, enhancement of N-methyl-D-aspartate (NMDA) receptor signalling has been proposed to underlie rt-PA-mediated neurotoxicity. However, the role of poly(ADP-ribose) polymerase-1 (PARP-1) activation, which mediates postischemic excitotoxic cell death, in rt-PA-mediated aggravation of ischemic brain injury has not been established and was therefore addressed in this study. After permanent focal cerebral ischemia, intravenous rt-PA application significantly increased early postischemic PARP-1 activation within ischemic hemispheres and infarct volumes compared with control mice without affecting cerebral blood flow. Rt-PA induced increase in PARP-1 activation, and infarct volumes could be blocked by the PARP inhibitor 3-aminobenzamide. Moreover, the rt-PA-induced increase in PARP-1 activation was also prevented by the NMDA antagonist MK-801. In summary, we demonstrate that rt-PA treatment enhances postischemic PARP-1 activation, which contributes to rt-PA induced aggravation of ischemic brain injury in vivo. Furthermore, we provide evidence that NMDA receptor activation is required for rt-PA-mediated effects on postischemic PARP-1 activation.

Topics: Animals; Benzamides; Blood Gas Analysis; Blood Pressure; Blood-Brain Barrier; Brain; Brain Infarction; Brain Ischemia; Dizocilpine Maleate; Enzyme Activation; Ischemic Attack, Transient; Male; Mice; Mice, Inbred C57BL; Poly (ADP-Ribose) Polymerase-1; Poly(ADP-ribose) Polymerase Inhibitors; Poly(ADP-ribose) Polymerases; Receptors, N-Methyl-D-Aspartate; Recombinant Proteins; Tissue Plasminogen Activator

Transient focal ischemia produced by local infusion of endothelin-1 (ET1) in the territory of the middle cerebral artery has been proposed as a potentially useful model for the screening of drugs developed for the treatment of thrombo-embolic stroke. However, most of the data rely exclusively on the assessment of the infarct volume, which is only a partial predictor of the neurological outcome of stroke. Here, we have validated the model using a multimodal approach for the assessment of neuroprotection, which includes (i) determination of the infarct volume by 2,3,5-triphenyltetrazolium chloride staining; (ii) an in-depth behavioral analysis of the neurological deficit; and (iii) an EEG analysis of electrophysiological abnormalities in the peri-infarct somatosensory forelimb cortical area, S1FL. The non-competitive NMDA receptor antagonist, MK-801 (3 mg/kg, injected i.p. 20 min after ET1 infusion in conscious rats) could reduce the infarct volume, reverse the EEG changes occurring at early times post-ET1, and markedly improve the neurological deficit in ischemic animals. The latter effect, however, was visible at day 3 post-ET1, because the drug itself produced substantial behavioral abnormalities at earlier times. We conclude that a multimodal approach can be applied to the ET1 model of focal ischemia, and that MK-801 can be used as a reference compound to which the activity of safer neuroprotective drugs should be compared.

Topics: Analysis of Variance; Animals; Behavior, Animal; Brain Infarction; Disease Models, Animal; Dizocilpine Maleate; Electroencephalography; Endothelin-1; Functional Laterality; Ischemic Attack, Transient; Male; Neuroprotective Agents; Rats; Rats, Wistar; Severity of Illness Index; Somatosensory Cortex; Tetrazolium Salts

PNQX (9-methyl-amino-6-nitro-hexahydro-benzo(F)quinoxalinedione) is a selective AMPA antagonist with demonstrated neuroprotective effects in focal ischemia in rats. Here we report corresponding effects in mouse hippocampal slice cultures subjected to oxygen and glucose deprivation (OGD) and in transient global cerebral ischemia in gerbils. For in vitro studies, hippocampal slice cultures derived from 7-day-old mice and grown for 14 days, were submersed in oxygen-glucose deprived medium for 30 min and exposed to PNQX for 24 h, starting together with OGD, immediately after OGD, or 2 h after OGD. For comparison, other cultures were exposed to the NMDA antagonist MK-801 using the same protocol. Both PNQX and MK-801 displayed significant neuroprotective effects in all hippocampal subfields when present during and after OGD. When added just after OGD, only PNQX retained some neuroprotective effect. When added 2 h after OGD neither PNQX nor MK-801 had an effect. Transient global cerebral ischemia was induced in Mongolian gerbils by occlusion of both common carotid arteries for 4.5 min, with PNQX (10 mg/kg) being injected i.p. 30, 60 and 90 min after the insult. Subsequent analysis of brain sections stained for the neurodegeneration marker Fluoro-Jade B and immunostained for the astroglial marker glial fibrillary acidic protein revealed a significant PNQX-induced decrease in neuronal cell death and astroglial activation. We conclude that, PNQX provided neuroprotection against both global cerebral ischemia in gerbils in vivo and oxygen-glucose deprivation in mouse hippocampal slice cultures.

Topics: Animals; Body Temperature; Cell Death; Coloring Agents; Dizocilpine Maleate; Excitatory Amino Acid Antagonists; Fluoresceins; Gerbillinae; Glucose; Hippocampus; Hypoxia, Brain; Ischemic Attack, Transient; Mice; Mice, Inbred C57BL; Microtubule-Associated Proteins; Nerve Degeneration; Neuroprotective Agents; Organ Culture Techniques; Organic Chemicals; Quinoxalines; Receptors, AMPA; Tolonium Chloride

The pre-ischaemic neuroprotective potential of a novel polyamine/NMDA antagonist N1-dansyl-spermine (1-5 mg kg(-1)) was studied in a transient focal cerebral ischaemia model in mice in comparison to a reference compound, MK-801 (1 or 3 mg kg(-1)). The intraluminal suture transient middle cerebral artery occlusion (MCAO) model was used. N1-dansyl-spermine and MK-801 were administered (i.p.) 30 min prior to ischaemia. A range of histological and behavioural assessments was employed. N1-dansyl-spermine had a comparable effect to MK-801 at reducing the percentage hemisphere lesion volume (%HLV) at the doses tested. Furthermore, N1-dansyl-spermine reduced the ischaemic brain oedema, which MK-801 did not. N1-dansyl-spermine significantly reversed the decrease of locomotor activity (LMA) caused by the MCAO and showed a significant effect at improving the rotarod performance impaired by MCAO. In contrast, MK-801 had no beneficial effect on sensorimotor function and even worsened the LMA. These results clearly demonstrate the pre-ischaemic neuroprotective effect of N1-dansyl-spermine in a transient focal cerebral ischaemia model.

Topics: Animals; Brain; Brain Edema; Dansyl Compounds; Disease Models, Animal; Dizocilpine Maleate; Dose-Response Relationship, Drug; Infarction, Middle Cerebral Artery; Ischemic Attack, Transient; Male; Mice; Motor Activity; Neuroprotective Agents; Rotarod Performance Test; Spermine; Tetrazolium Salts; Time Factors

MK-801 is a noncompetitive antagonist of N-methyl-d-aspartate subtype glutamate receptors with protective efficacy in experimental stroke. This study examined the impact of MK-801 on cerebral blood flow (CBF) and its relationship to gene expression changes during focal ischemia.. Spontaneously hypertensive rats were subjected to surgical occlusion of the middle cerebral artery and ipsilateral common carotid artery after 30 minutes pretreatment with 5 mg/kg MK-801 or saline vehicle. After 2.5 hours of ischemia, regional CBF was evaluated by [14C]iodoantipyrine autoradiography and compared with distributions of gene expression changes evaluated by in situ hybridization detection of mRNAs encoding several immediate-early genes and the stress protein, hsp72.. MK-801 increased CBF in contralateral cortex from 93+/-15 to 187+/-37 mL/100 g per minute and produced a significant 25% reduction in the volume of ischemic cortex ipsilateral to occlusion. The extent of cortex failing to express inducible mRNAs correspondingly decreased, but the CBF threshold for mRNA synthesis remained unchanged (25 to 30 mL/100 g per minute). Widespread immediate-early gene expression in the neocortex became restricted to periinfarct regions after MK-801 treatment, and hybridization patterns in the striatum and hippocampus reflected the altered topography of cortical activation after drug treatment.. MK-801 alters ischemia-induced gene expression by 2 distinct mechanisms. Generalized increases in CBF reduce the volume of cortex falling below ischemic injury thresholds, protecting tissue and facilitating transcription of inducible genes proximal to the ischemic focus. In addition, MK-801 attenuates the signals that induce expression of immediate-early genes in cortical and subcortical regions remote from the middle cerebral artery territory.

Topics: Animals; Blood Circulation Time; Cerebrovascular Circulation; Dizocilpine Maleate; Gene Expression Regulation; Genes, Immediate-Early; Hippocampus; In Situ Hybridization; Ischemia; Ischemic Attack, Transient; Middle Cerebral Artery; Neurons; Neuroprotective Agents; Rats; Rats, Inbred SHR; Receptors, N-Methyl-D-Aspartate; RNA, Messenger; Signal Transduction; Time Factors

The present study evaluated the potential effect of geranylgeranylacetone (GGA), which is known as an antiulcer agent, against the delayed neuronal death (DND) of hippocampal neurons an otherwise lethal ischemic insult. Pretreatment with single oral GGA (800 mg/kg, 2 days before ischemia) significantly attenuated DND in gerbil hippocampus. These effects of GGA were prevented by the coinjection of MK801, a noncompetitive N-methyl-d-aspartate glutamate receptor antagonist, which indicates that the protection was indeed glutamate receptor activation mediated.

Topics: Administration, Oral; Animals; Cell Death; Diterpenes; Dizocilpine Maleate; Drug Administration Schedule; Drug Antagonism; Excitatory Amino Acid Antagonists; Gerbillinae; Hippocampus; Ischemic Attack, Transient; Male; Neurons; Neuroprotective Agents; Receptors, N-Methyl-D-Aspartate; Time Factors

N-Methyl-D-aspartate receptor antagonism contributes to the anesthetic action of nitrous oxide (N(2)O). We examined the effects of the N-methyl-D-aspartate antagonists N(2)O and dizocilpine on outcome from filament occlusion of the middle cerebral artery (MCAO). Rats breathed 70% nitrogen/30% oxygen or 70% N(2)O/30% oxygen during MCAO. A third group breathed 70% nitrogen/30% oxygen and was given dizocilpine (0.25 mg/kg IV). After 75 min of MCAO, the rats recovered for 3 or 14 days. Pericranial temperature was maintained at 37.5 degrees C +/- 0.2 degrees C during ischemia and for 20 h postischemia. N(2)O did not alter neurologic scores at 3 days (N(2)O, 21 +/- 6; nitrogen, 22 +/- 8; P = 0.95; 0 = normal; 48 = maximal deficit; mean +/- sd; n = 15) or 14 days (N(2)O, 13 +/- 6; nitrogen, 12 +/- 6; P = 0.93; n = 15-16) postischemia. N(2)O had no effect on infarct size at 3 days (N(2)O, 162 +/- 45 mm(3); nitrogen, 162 +/- 61 mm(3); P > 0.99) or 14 days (N(2)O, 147 +/- 56 mm(3); nitrogen, 151 +/- 62 mm(3); P = 0.99) postischemia. Dizocilpine treatment caused smaller infarcts (3 days: 66 +/- 49 mm(3), P < 0.0001 versus nitrogen; 14 days: 84 +/- 50 mm(3), P < 0.006 versus nitrogen) and reduced the neurologic deficit (3 days: 10 +/- 10, P = 0.002 versus nitrogen; 14 days: 6 +/- 7, P = 0.006 versus nitrogen). N(2)O (70%) had no effect on either behavioral or histologic outcome from transient focal cerebral ischemia when compared with results in rats breathing 70% nitrogen. These results indicate that normobaric N(2)O does not alter the response of rat brain to a focal ischemic insult.

Topics: Animals; Blood Pressure; Dizocilpine Maleate; Intubation, Intratracheal; Ischemic Attack, Transient; Male; Nitrous Oxide; Rats; Rats, Wistar; Receptors, N-Methyl-D-Aspartate; Regression Analysis

Computer-assisted procedures are used to measure infarct areas in animal stroke models, but this approach usually follows the less objective manual tracing of the boundaries of the infarct. Building on previously reported methodology using scanned images of triphenyltetrazolium chloride (TTC)-stained rat brains in the intraluminal thread model, we developed an objective method to assess ischemic damage in both the mouse and rat brains. The unique addition to our approach is the use of sham-treated animals, which thereby permits the removal of normal brain white matter from the ipsilateral injured brain. All brain sections per animal were scanned simultaneously using a Microtek Scanmaker 4 flatbed scanner. Color segmentation on full color images of 2 mm coronal brain sections was performed. Using Image Pro Plus (4.0) and color segmentation, ischemic and normal white matter areas were measured in the green channel and the entire brain area in the red channel. The percent of unstained tissue was calculated for sham-treated animals and for those with cerebral ischemia. By subtracting the average unstained area of the sham-treated group from the average unstained area from the ischemic group, the ischemic area was calculated. This methodology was validated using mouse and rat permanent and transient, focal ischemia models and MK-801 in the permanent ischemia models. MK-801, dosed at 3 mg/kg i.p. prior to the injury, reduced the injury by 75% in the mouse and 44% in the rat permanent occlusion models. The benefits of this methodology include: objectivity of the analysis of the ischemic injury, use of readily available software so that costs can be contained and removal of normal subcortical white matter from the calculation. This method should allow more consistent evaluation of changes in the infarct size, therefore, resulting in reduced variability and higher productivity.

Topics: Animals; Brain Infarction; Brain Ischemia; Carotid Arteries; Coloring Agents; Diagnostic Imaging; Disease Models, Animal; Dizocilpine Maleate; Image Processing, Computer-Assisted; Ischemic Attack, Transient; Laser-Doppler Flowmetry; Male; Mice; Mice, Inbred C57BL; Neuroprotective Agents; Rats; Rats, Sprague-Dawley; Stroke

Growth associated protein-43 (GAP-43) gene induction may be involved in reactive events that follow cerebral ischemic damage. Antagonists of the N-methyl-D-aspartate (NMDA) subclass of glutamate receptors are thought to ameliorate functional outcome after ischemic injury. To assess whether glutamate NMDA receptor blockade could alter GAP-43 postischemic induction we performed immunocytochemistry in rat brains that had been subjected to middle cerebral artery occlusion. Cortical cells did not constitutively express GAP-43, yet focal ischemia induced its expression, with an intense signal generated in cells over the lesioned area at 6 h, increasing at 24 h postischemia. This signal was effectively decreased by pretreatment with the NMDA receptor antagonist (5R,10S)-(+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]-cyclohepten-5,10-imine hydrogen maleate (0.1 mg/kg s.c.), but not by the glutamate release blocker riluzole (8 mg/kg i.v.), suggesting that overactivation of NMDA receptor during ischemia is linked to GAP-43 expression.

Topics: Animals; Brain; Dizocilpine Maleate; Excitatory Amino Acid Antagonists; GAP-43 Protein; Gene Expression Regulation; Immunohistochemistry; Ischemic Attack, Transient; Neuroprotective Agents; Rats; Receptors, N-Methyl-D-Aspartate; Riluzole; Time Factors; Transcriptional Activation

We performed real-time monitoring of the extracellular glutamate dynamics in the rat striatum in vivo using the microdialysis electrode technique, during an experimental penumbral condition of moderate global cerebral ischemia and activated glutamate receptors. The local cerebral blood flow (CBF) was measured with a laser-Doppler probe. One minute after bilateral common carotid artery occlusion (BCAO), CBF was reduced to approximately 60% of the pre-ischemic value and it remained at this level during the period of occlusion. After BCAO, a transient depolarization and a transient increase in extracellular glutamate concentration ([Glu]e) were seen. In other rats, 500 microM N-methyl-D-aspartate (NMDA) was locally micro-transfused for 30 min prior to BCAO. Upon induction of BCAO, an anoxic depolarization-like depolarization and a gradual increase in [Glu]e that continued over the duration of BCAO were seen. After BCAO was terminated, the direct current (DC) rapidly recovered to the basal level, while [Glu]e gradually decreased to the basal level. In rats that were locally micro-transfused with 500 microM Kainate prior to BCAO, DC and [Glu]e did not differ significantly from control. Pretreatment with MK-801 prior to NMDA treatment completely inhibited the NMDA-induced changes in DC and [Glu]e. Pretreatment with NBQX prior to NMDA treatment did not inhibit the NMDA-induced changes in DC and [Glu]e. Consequently, we found that activation of NMDA receptors by elevated [Glu]e exerts an important effect on [Glu]e dynamics in the spreading stroke region very early in the acute stage of cerebral ischemia in vivo.

Topics: Animals; Carotid Artery, Common; Cerebrovascular Circulation; Corpus Striatum; Dizocilpine Maleate; Excitatory Amino Acid Agonists; Excitatory Amino Acid Antagonists; Extracellular Space; Glutamic Acid; Ischemic Attack, Transient; Kainic Acid; Male; Microdialysis; N-Methylaspartate; Rats; Rats, Wistar; Receptors, Glutamate; Stroke

In a recent study of focal cerebral ischemia in rats, pre-ischemic administration of the synthetic allosteric hemoglobin modifier RSR13 (2-[4-[[3,5-dimethylanilino) carbonyl] methyl] phenoxy]-2-methylproprionic acid) reduced cerebral infarct size when combined with the NMDA receptor antagonist dizocilpine (MK-801) but not when given alone. We hypothesized that post-ischemic RSR13 administration would enhance neuroprotection afforded by NMDA receptor antagonism in a rat model of transient middle cerebral artery occlusion (MCAO). Fasted normothermic Wistar rats underwent 75 min of temporary MCAO. At onset of reperfusion, rats randomly received: (1) 0.9% NaCl (vehicle) i.v. alone (n=16); (2) 0.9% NaCl+dizocilpine (0.25 mg/kg) i.v. (n=16); or (3) RSR13 (150 mg/kg)+dizocilpine (0.25 mg/kg) i.v. (n=17). Seven days later, neurologic deficit and cerebral infarct size were determined. Dizocilpine alone compared to vehicle reduced mean+/-S.D. subcortical (52+/-24 mm(3) vs. 122+/-64 mm(3), P=0.003) and cortical (35+/-35 mm(3) vs. 125+/-72 mm(3), P=0.00074) infarct volumes. When compared to dizocilpine alone, the combination of RSR13+dizocilpine further reduced subcortical (37+/-14 mm(3) vs. 52+/-24 mm(3), P=0. 034) and cortical (8+/-19 mm(3) vs. 35+/-35 mm(3), P=0.018) infarct size. RSR13+dizocilpine improved neurologic scores vs. either dizocilpine alone (P=0.0014) or vehicle (P=10(-7)). The combination of NMDA receptor antagonism and a RSR13 mediated rightward shift of the oxy-hemoglobin dissociation curve improved outcome from MCAO. Because this occurred after reperfusion, our results suggest that the post-ischemic brain continues to suffer from hypoperfusion defects, which are amenable to therapy by enhanced O(2) delivery. The results also support the concept that neuroprotective strategies, which combine drugs with different mechanisms of action, may yield cumulative benefits.

Topics: Aniline Compounds; Animals; Blood Gas Analysis; Body Temperature; Disease Models, Animal; Dizocilpine Maleate; Drug Synergism; Hemoglobins; Infarction, Middle Cerebral Artery; Ischemic Attack, Transient; Male; Neurologic Examination; Neuroprotective Agents; Propionates; Rats; Rats, Wistar; Receptors, N-Methyl-D-Aspartate

Dynamic changes in the regional cerebral glucose metabolic rate induced by hypoxia/reoxygenation or ischemia/reperfusion were investigated with a positron autoradiography technique. Fresh rat brain slices were incubated with [18F]2-fluoro-2-deoxy-D-glucose ([18F]FDG) in oxygenated Krebs-Ringer solution at 36 degrees C, and serial two-dimensional time-resolved images of [18F]FDG uptake in the slices were obtained. In the case of loading hypoxia (oxygen deprivation)/pseudoischemia (oxygen and glucose deprivation) for various periods of time, the net influx constant (K) of [18F]FDG at preloading and after reoxygenation/pseudoreperfusion (post-loading) was quantitatively evaluated by applying the Patlak graphical method to the image data. Regardless of the brain region, with hypoxia lasting > or =20 minutes, the postloading K value was decreased compared with the unloaded control, whereas with pseudoischemia of < or =40 minutes, approximately the same level as the unloaded control was maintained. Next, the neuroprotective effect against hypoxia/pseudoischemia loading induced by the addition of a free radical scavenger or an N-methyl-D-aspartate (NMDA) antagonist was assessed by determining whether a decrease in the postloading K value was prevented. Whereas with 20-minute hypoxia, both agents exhibited a neuroprotective effect, in the case of 50-minute pseudoischemia, only the NMDA antagonist did so, with the free radical scavenger being ineffective. These results demonstrate that hypoxia causes irreversible neuronal damage within a shorter period than ischemia, with both free radicals and glutamate suggested to be involved in tandem in the neurotoxicity induced by hypoxia, whereas glutamate alone is involved in ischemic neurotoxicity.

Topics: Animals; Autoradiography; Brain; Cerebrovascular Circulation; Cyclic N-Oxides; Dizocilpine Maleate; Excitatory Amino Acid Antagonists; Fluorodeoxyglucose F18; Free Radicals; Glucose; Glutamic Acid; Hypoxia, Brain; In Vitro Techniques; Ischemic Attack, Transient; Male; Neurotoxins; Nitrogen Oxides; Oxygen; Radionuclide Imaging; Rats; Rats, Sprague-Dawley; Reperfusion Injury; Spin Labels

Glutamic acid, an excitatory amino acid, has been proposed to play a major deleterious influence in cerebral ischemia. However, the neuroprotective activity of various glutamate receptor antagonists is often low or absent, according to the animal model used. In the present study, we examined the effect of several antagonists acting on glutamate receptors of the N-methyl-D-aspartate (NMDA) type in rats submitted to a brief (5 minutes) global cerebral ischemia. The different compounds used were poorly active or inactive on behavioural and histologic alterations induced by ischemia. Our results suggest that, in this model, overactivation of NMDA receptor complex does not play a predominant role in the pathogenesis of ischemic brain damage.

Topics: Animals; Brain; Dizocilpine Maleate; Excitatory Amino Acid Antagonists; Ischemic Attack, Transient; Kynurenic Acid; Male; Motor Activity; Rats; Rats, Wistar; Receptors, Glutamate; Receptors, N-Methyl-D-Aspartate; Time Factors

The aim of the study was to examine the role of NMDA receptors in modulation of protective effect against bicuculline toxicity after transient brain ischemia in mice. Animals were exposed for 30 min to bilateral clamping of the common carotid arteries (BCCA) in anaesthesia. MK-801 was administered intraperitoneally in two paradigms: a) acute treatment: twice, 1.0 mg/kg; 1 hour before clamping and 6 hours after re-circulation and b) chronic treatment: 0.1 mg/kg; started 24 hours after re-circulation and continued once daily for 13 days, the last injection was administered 24 hours before seizure induction. 14 days after BCCA, the animals were injected with bicuculline (3.5 mg/kg s.c). A significant decrease in seizure susceptibility could be observed in BCCA treated mice compared with sham-operated controls. Acute treatment with MK-801 did not affect seizure activity both in sham and BCCA mice. Chronic treatment with the drug potentiated anticonvulsant effect of brain ischemia but had no influence on seizure activity in sham-operated mice. The analysis of GABA content in brain tissue performed 14 days after BCCA showed a moderate increase in vehicle-treated mice and significant elevation after chronic treatment with MK-801. It can be suggested that NMDA receptors are not involved in the induction of a protective effect against bicuculline toxicity after transient brain ischemia. The prolonged treatment with low doses of MK-801 may potentiate a developed process in a mechanism of chemical preconditioning.

Topics: Age Factors; Animals; Behavior, Animal; Bicuculline; Brain Chemistry; Convulsants; Dizocilpine Maleate; Epilepsy; Excitatory Amino Acid Antagonists; gamma-Aminobutyric Acid; Ischemic Attack, Transient; Ischemic Preconditioning; Male; Mice; Receptors, N-Methyl-D-Aspartate; Seizures; Survival Rate

Inappropriate activation of NMDA receptors during a period of cerebral ischaemia is a crucial event in the pathway leading to neuronal degeneration. However, significant research has failed to deliver a clinically active NMDA receptor antagonist, and competitive NMDA antagonists are ineffective in many experimental models of ischaemia. The NMDA receptor itself has a number of modulatory sites which may affect receptor function under ischaemic conditions. Using rat organotypic hippocampal slice cultures we have investigated whether the redox modulatory site affects the neuroprotective efficacy of NMDA receptor antagonists against excitotoxicity and experimental ischaemia (OGD). NMDA toxicity was significantly enhanced in cultures pretreated with a reducing agent. The noncompetitive antagonist MK-801 and a glycine-site blocker were equally neuroprotective in both normal and reduced conditions, but there was a significant rightward shift in the dose-response curves of the competitive antagonists APV and CPP and the uncompetitive antagonist memantine. OGD produced neuronal damage predominantly in the CA1 region, which was prevented by MK-801 and memantine, but not by APV or CPP. Inclusion of an oxidizing agent during the period of OGD had no effect alone, but significantly enhanced the neuroprotective potency of the competitive antagonists. These data clearly demonstrate that chemical reduction of the redox modulatory site of the NMDA receptor decreases the ability of competitive antagonists to block NMDA receptor-mediated neuronal damage, and that the reducing conditions which occur during simulated ischaemia are sufficient to produce a similar effect. This may have important implications for the design of future neuroprotective agents.

Topics: 2-Amino-5-phosphonovalerate; Animals; Dithionitrobenzoic Acid; Dithiothreitol; Dizocilpine Maleate; Excitatory Amino Acid Antagonists; Hippocampus; Ischemic Attack, Transient; Memantine; N-Methylaspartate; Neurons; Neuroprotective Agents; Organ Culture Techniques; Piperazines; Rats; Rats, Wistar; Receptors, N-Methyl-D-Aspartate

The stereoselective synthesis and biological activity of NPS 1407 (4a), (S)-(-)-3-amino-1,1-bis(3-fluorophenyl)butane, a potent, stereoselective antagonist of the NMDA receptor, are described. The racemate (4) was found to be active at the NMDA receptor in an in vitro assay, prompting the synthesis of the individual stereoisomers. The S isomer (4a) was found to be 12 times more potent than the R isomer (4b). Compound 4a demonstrated in vivo pharmacological activity in neuroprotection and anticonvulsant assays.

Topics: Animals; Anticonvulsants; Cerebellum; Dizocilpine Maleate; Excitatory Amino Acid Antagonists; Ischemic Attack, Transient; Mice; Molecular Structure; Neuroprotective Agents; Rats; Receptors, N-Methyl-D-Aspartate; Seizures; Stereoisomerism

In the present studies, we have examined the effects of two new Ca(2+) channel blockers, LY042826 (N-[2-[(2-methylphenyl)(phenyl)methoxy]ethyl]-1-butanamine hydrochloride) and LY393615 (N-[[5, 5-bis(4-fluorophenyl)tetrahydro-2-furanyl]methyl]-1-butanamine hydrochloride) in the gerbil model of global and the endothelin-1 rat model of focal cerebral ischaemia in vivo. Results indicated that both LY042826 (P<0.01) and LY393615 (P<0.001) provided significant protection against ischaemia-induced hippocampal damage in global cerebral ischaemia when dosed at 15 mg/kg i.p. 30 min before and 2 h 30 min after occlusion. In further studies, LY042826 (P<0.05) and LY393615 (P<0.01) were also protective when administered at 15 mg/kg i.p. immediately after and 3 h post-occlusion. Both compounds also provided a significant reduction in the infarct volume following endothelin-1 middle cerebral artery occlusion in the rat when administered at 15 mg/kg i.p. immediately (P<0.05) after occlusion. This protection was similar to that observed with the NMDA receptor antagonist (5R,10S)-(+)-5-methyl-10, 11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine), MK-801 in this model. In conclusion and as a result of the present studies, we report that the novel Ca(2+) channel blockers, LY042826 and LY393615 protect against ischaemia-induced brain injury in gerbils and rats. The compounds were neuroprotective when administered post-occlusion and may therefore be useful anti-ischaemic agents.

Topics: Animals; Biphenyl Compounds; Butylamines; Calcium Channel Blockers; Cell Count; Dizocilpine Maleate; Endothelin-1; Furans; Gerbillinae; Guanidines; Hippocampus; Ischemic Attack, Transient; Male; Neurons; Neuroprotective Agents; Piperidines

Muscarinic and NMDA receptors contribute to post-traumatic hypersensitivity to secondary ischemia. However, the effect of these receptor antagonists on behavior and CA1 neuronal death after traumatic brain injury (TBI) with acute (1 h after TBI) forebrain ischemia has not been systematically assessed. We examined cognitive and motor dysfunction and the relationship of behavior deficits to neuronal death in this model using muscarinic and NMDA antagonists. Three behavioral groups (n=10/group) of Wistar rats were subjected to mild TBI and 6 min of forebrain ischemia imposed 1 h after TBI with 45 days survival. Motor and spatial memory performance were assessed using the rotarod task and Morris water maze. Seven additional groups (n=6/group) were evaluated only for CA1 death after 7 days survival following sham, individual or combined injury with and without drug treatments. Rats were given 0.3 mg/kg MK-801 (M) and 1.0 mg/kg scopolamine (S) alone or combined (M-S) before or 45 min after TBI. Rotarod performance was tested at days 1-5 and maze performance on days 11-15 and 40-44 after M-S treatment. The 7-day studies showed M-S treatment (p<0.01) reduced CA1 neuronal death better than either S or M alone. Behavioral groups had inadvertent post-ischemic hypothermia that decreased CA1 death and likely influenced behavioral morbidity. M-S given before TBI (p<0.01) decreased memory deficits on day 15, while M-S treatment given after TBI was ineffective. Unexpectedly, M-S treatment before or after TBI produced transient motor deficits (p<0. 01). Memory improvement occurred independent of CA1 death.

Topics: Animals; Body Weight; Brain Injuries; Combined Modality Therapy; Dizocilpine Maleate; Excitatory Amino Acid Antagonists; Ischemic Attack, Transient; Male; Maze Learning; Muscarinic Antagonists; Psychomotor Performance; Rats; Rats, Wistar; Scopolamine; Treatment Outcome

This work determined Ca2+ transport processes that contribute to the rise in cytosolic Ca2+ during in vitro ischemia (deprivation of oxygen and glucose) in the hippocampus. The CA1 striatum radiatum of rat hippocampal slices was monitored by confocal microscopy of calcium green-1. There was a 50-60% increase in fluorescence during 10 min of ischemia after a 3 min lag period. During the first 5 min of ischemia the major contribution was from Ca2+ entering via NMDA receptors; most of the fluorescence increase was blocked by MK-801. Approximately one-half of the sustained increase in fluorescence during 10 min of ischemia was caused by activation of Ca2+ release from mitochondria via the mitochondrial 2Na+-Ca2+ exchanger. Inhibition of Na+ influx across the plasmalemma using lidocaine, low extracellular Na+, or the AMPA/kainate receptor blocker CNQX reduced the fluorescence increase by 50%. The 2Na+-Ca2+ exchange blocker CGP37157 also blocked the increase, and this effect was not additive with the effects of blocking Na+ influx. When added together, CNQX and lidocaine inhibited the fluorescence increase more than CGP37157 did. Thus, during ischemia, Ca2+ entry via NMDA receptors accounts for the earliest rise in cytosolic Ca2+. Approximately 50% of the sustained rise is attributable to Na+ entry and subsequent Ca2+ release from the mitochondria via the 2Na+-Ca2+ exchanger. Sodium entry is also hypothesized to compromise clearance of cytosolic Ca2+ by routes other than mitochondrial uptake, probably by enhancing ATP depletion, accounting for the large inhibition of the Ca2+ increase by the combination of CNQX and lidocaine.

Topics: Animals; Calcium; Cytosol; Dizocilpine Maleate; Glutamic Acid; Hippocampus; In Vitro Techniques; Ischemic Attack, Transient; Kinetics; Lidocaine; Male; Mitochondria; N-Methylaspartate; Pyramidal Cells; Rats; Rats, Sprague-Dawley; Sodium; Sodium-Calcium Exchanger; Time Factors

This study examined the effect of a pharmacologically induced rightward shift in the partial pressure of oxygen at which 50% of hemoglobin is saturated (P50) on outcome from transient focal cerebral ischemia in the rat. Halothane anesthetized rats (n=20 per group) were given saline or a single 15-min infusion of 150 mg/kg RSR13 (2-[4-[[3,5-dimethylanilino) carbonyl]methyl]phenoxy]-2-methylproprionic acid) intravenously before or 30 min after onset of 75 min of middle cerebral artery filament occlusion (MCAO). Seven days later, severity of hemiparesis and cerebral infarct size were examined. RSR13 alone did not significantly improve outcome. Conscious normothermic rats (n=12 per group) were also given RSR13 (150 mg/kg) or 0.9% NaCl intravenously and subjected to 75 min of MCAO with 7 days of recovery. Again, RSR13 alone did not significantly reduce infarct size or improve neurologic score. A dose-response curve for dizocilpine (MK-801) was then constructed in conscious normothermic rats subjected to 75 min of MCAO. Dizocilpine (0.5 mg/kg i.v.) caused a 90% reduction in mean infarct size while 0.25 mg/kg reduced infarct size by 48%. Other rats were then subjected to 75 min of MCAO after being given dizocilpine (0.25 mg/kg i.v.; n=18) or RSR13 (150 mg/kg i.v. )+dizocilpine (0.25 mg/kg i.v.; n=15). RSR13+dizocilpine resulted in smaller cortical infarct volume (8+/-14 mm3 vs. 34+/-37 mm3, p<0.02) and total cerebral infarct volume (46+/-28 mm3 vs. 81+/-60 mm3, p<0. 05) compared to dizocilpine alone, respectively. We conclude that a pre-ischemic peak increase in P50 of approximately 25 mmHg alone is insufficient to reduce focal ischemic injury, but may be advantageous when used in conjunction with other neuroprotective agents.

Topics: Allosteric Site; Aniline Compounds; Animals; Antisickling Agents; Blood Gas Analysis; Body Temperature; Brain Chemistry; Cerebral Cortex; Cerebral Infarction; Dizocilpine Maleate; Drug Therapy, Combination; Excitatory Amino Acid Antagonists; Hemoglobins; Ischemic Attack, Transient; Male; Propionates; Rats; Rats, Wistar; Receptors, N-Methyl-D-Aspartate

This study examined microglial responses after photochemically induced focal ischemia of the rat cortex. Microglial activation exceeded by far the area of the ischemic lesion. Based on morphological criteria and expression of immunomolecules three distinct patterns could be distinguished. (1) In the infarct core and the border zone microglia transformed into phagocytes and removed debris with the aid of hematogeneous macrophages. Exclusively in this area a subpopulation of CD8+ microglia/mnacrophages was present. (2) In secondarily degenerating fibre tracts and nuclei with retrograde neuronal loss, microglia were activated with a delay of days and showed increased expression of complement receptor 3, major histocompatibility complex class II and CD4 molecules, but only low phagocytic activity. (3) In remote ipsilateral cortex devoid of neuronal damage, microglia transiently responded by increased complement receptor 3, but not by major histocompatibility complex class II and CD4 expression. Furthermore, the total number of microglia had increased. This remote response could partly be blocked by dizocilpine maleate, a non-competitive N-methyl-D-aspartate receptor antagonist, implicating a functional role of spreading depression. Taken together, our findings point to a tight and differential regulation of microglial responses in the infarct core, degenerating fibre tracts and remote brain regions without neuronal loss.

Topics: Animals; Antibodies, Monoclonal; Cerebral Cortex; Cerebral Infarction; Dizocilpine Maleate; Functional Laterality; Immunohistochemistry; Ischemic Attack, Transient; Microglia; Photochemistry; Rats; Rats, Wistar; Rose Bengal; Time Factors

Rats were subjected to incomplete cerebral ischemia induced by occlusion of common carotid arteries for 30 min, and subsequent reperfusion for 15 min. The concentrations of reduced glutathione (GSH), malondialdehyde (MDA) and superoxide dismutase (SOD) activity were determined in the dorsal hippocampus in order to evaluate their changes during ischemia and reperfusion following ischemia. The depletion of GSH was observed during ischemia with a further depletion during post-ischemic reperfusion (P < 0.001), while a significant increase in SOD activity and MDA levels was found only after reperfusion following ischemia (P < 0.001). Animals in which ischemia was followed by reperfusion were treated with a non-competitive NMDA receptor antagonist, MK-801 (1 mg/kg, i.v.), and a radical scavenger, U-83836E (5 mg/kg, i.v.), prior to ischemia. Although a full recovery of GSH levels was not observed following MK-801 and U-83836E pretreatment as compared to control (P < 0.05), MK-801 was more potent than U-83836E in the partial protection of the GSH pool (P < 0.05 and P < 0.01, respectively). The rise in SOD activity and MDA level were brought close to those of control due to the effects of both MK-801 and U-83836E (P > 0.05). In conclusion, the tissue changes in GSH concentrations evoked by ischemia and reperfusion were partially prevented by the effects of both drugs, MK-801 having the greater effect. This suggests that the NMDA receptor activation may play a role in the generation of reactive oxygen species. On the other hand, the inhibition of lipid peroxidation brought about by both MK-801 or U-83836E suggests the therapeutic efficiency of these agents in ischemia/reperfusion injury.

Topics: Animals; Antioxidants; Chromans; Dizocilpine Maleate; Glutathione; Hippocampus; Ischemic Attack, Transient; Male; Malondialdehyde; Neuroprotective Agents; Piperazines; Rats; Rats, Sprague-Dawley; Reperfusion Injury; Superoxide Dismutase

The effect of middle cerebral artery (MCA) occlusion on the activity-regulated cytoskeleton-associated protein (Arc) mRNA expression has been investigated using in situ hybridization. It was induced in the extensive regions of cerebral cortex, medial striatum, and distant areas such as the ipsilateral lateral septal nucleus, bilateral hippocampal formation and contralateral amygdala following MCA occlusion. In the hippocampal formation, it was induced in the granule cell layer and the stratum pyramidale at 1 h and in the molecular layer and in the stratum oriens and stratum radiatum bilaterally at 4 h. MK-801 pretreatment strongly attenuated the induction of Arc mRNA. The present results suggest that Arc may play an important role in the neuronal plasticity through NMDA activation following focal cerebral ischemia.

Topics: Animals; Arterial Occlusive Diseases; Autoradiography; Cytoskeletal Proteins; Dendrites; Dizocilpine Maleate; DNA Probes; Excitatory Amino Acid Antagonists; Genes, Immediate-Early; In Situ Hybridization; Ischemic Attack, Transient; Male; Middle Cerebral Artery; Nerve Tissue Proteins; Rats; Rats, Sprague-Dawley; RNA, Messenger

In order to study the role of metabotropic glutamate 1 (mGlu1) receptors in ischemic neuronal death, we examined the effects of the recently characterized and relatively selective mGlu1 receptor antagonists 1-aminoindan-1,5-dicarboxylic acid (AIDA) and (S)-(+)-2-(3'-carboxybicyclo[1.1.1]pentyl)-glycine (CBPG) in murine cortical cell cultures and rat organotypic hippocampal slices exposed to oxygen glucose deprivation (OGD) and in vivo, following transient global ischemia in gerbils. AIDA and CBPG significantly reduced neuronal death when added to the incubation medium during the OGD insult and the subsequent recovery period. Neuroprotection was observed even when these compounds were added up to 60 min (in cortical neurons) or 30 min (in hippocampal slices) after OGD. In vivo, i.c.v. administration of AIDA and CBPG reduced hippocampal CA1 pyramidal cell injury following transient global ischemia. Neuroprotection was also observed when AIDA was added to the hippocampal perfusion fluid in microdialysis experiments, and this effect was associated with an increase in the basal output of GABA. These findings demonstrate that AIDA and CBPG are neuroprotective when administered during the maturation of ischemic damage and that different mechanisms are likely to be involved in mediating their effects following blockade of mGlu1 receptors in cortical and hippocampal neurons.

Topics: Animals; Bridged Bicyclo Compounds; Cell Hypoxia; Cells, Cultured; Cerebral Cortex; Coculture Techniques; Dizocilpine Maleate; Excitatory Amino Acid Antagonists; Fetus; Gerbillinae; Glucose; Glycine; Hippocampus; Indans; Ischemic Attack, Transient; Mice; Neuroglia; Neurons; Neuroprotective Agents; Rats; Receptors, Metabotropic Glutamate

A double-tracer autoradiographic method for simultaneous measurement of regional glucose utilization (rCMRglc) and regional protein synthesis (PS) in consecutive brain sections is described and applied to study the metabolism of the ischemic penumbra 2 h after occlusion of the middle cerebral artery (MCAO) in rats. In halothane anesthesia, the left middle cerebral artery was permanently occluded. Two hours after MCAO an i.v. bolus injection of 14C-deoxyglucose and 3H-leucine was given and circulated for 45 min. Two sets of brain sections were processed for quantitative autoradiography. Neighboring brain sections exposed an X-ray film (3H-insensitive), and a 3H-sensitive for determination of rCMRglc and PS, respectively. Sections for PS determination were washed in trichloroacetic acid (TCA) prior to film exposure in order to remove 14C-deoxyglucose and unincorporated 3H-leucine. Regional rates of PS and glucose utilization were measured by densitometric image analysis. Normal rates of metabolism were defined as mean +/- 2 SD of values in the non-ischemic cortex. The volumes of ischemic cortex displaying normal rates of PS and glucose utilization, respectively, were measured. The cortical volume with normal PS was significantly less than that of normal rCMRglc: 142 (127-147) mm3 vs. 203 (184-206) mm3. Treatment with the glutamate antagonists MK-801 (1 mg kg-1) and NBQX (30 mg kg-1 x 2) did not significantly change this, although MK-801 tended to reduce the size of the metabolic penumbra calculated as the difference between ischemic cortex with reduced PS and ischemic cortex with reduced rCMRglc.

Topics: Animals; Autoradiography; Blood Pressure; Brain; Carbon Radioisotopes; Deoxyglucose; Dizocilpine Maleate; Excitatory Amino Acid Antagonists; Glucose; Ischemic Attack, Transient; Leucine; Male; Nerve Tissue Proteins; Quinoxalines; Radioisotope Dilution Technique; Rats; Rats, Wistar; Reference Values; Tritium

Metabotropic glutamate (mGlu) receptors have been implicated in a number of physiological and pathological responses to glutamate, but the exact role of group I mGlu receptors in causing postischaemic injury is not yet clear. In this study, we examined whether the recently-characterized and relatively selective mGlu1 receptor antagonists 1-aminoindan-1,5-dicarboxylic acid (AIDA) and (S)-(+)-2-(3'-carboxybicyclo[1.1.1]pentyl)-glycine (CBPG) could reduce neuronal death in vitro, following oxygen-glucose deprivation (OGD) in murine cortical cell and rat organotypic hippocampal cultures, and in vivo, after global ischaemia in gerbils. When present in the incubation medium during the OGD insult and the subsequent 24 h recovery period, AIDA and CBPG significantly reduced neuronal death in vitro. The extent of protection was similar to that observed with the nonselective mGlu receptor antagonist (+)-alpha-methyl-4-carboxyphenylglycine [(+)MCPG] and with typical ionotropic glutamate (iGlu) receptor antagonists. Neuroprotection was also observed when AIDA or CBPG were added only after the OGD insult was terminated. Neuronal injury was not attenuated by the inactive isomer (-)MCPG, but was significantly enhanced by the nonselective mGlu receptor agonist (1S,3R)-1-aminocyclopentane-1, 3-dicarboxylic acid [(1S,3R)-ACPD] and the group I mGlu receptor agonist 3,5-dihydroxyphenylglycine (3,5-DHPG). The antagonists (+)MCPG, AIDA and CBPG were also neuroprotective in vivo, because i. c.v. administration reduced CA1 pyramidal cell degeneration examined 7 days following transient carotid occlusion in gerbils. Our results point to a role of mGlu1 receptors in the pathological mechanisms responsible for postischaemic neuronal death and propose a new target for neuroprotection.

Topics: Animals; Animals, Newborn; Astrocytes; Benzoates; Bridged Bicyclo Compounds; Cell Death; Cells, Cultured; Cerebral Cortex; Dizocilpine Maleate; Excitatory Amino Acid Antagonists; Gerbillinae; Glycine; Indans; Ischemic Attack, Transient; Mice; Neuroprotective Agents; Neurotoxins; Organ Culture Techniques; Pyramidal Cells; Quinoxalines; Receptors, Metabotropic Glutamate; Resorcinols

Repetitive transient ischemic depolarizations (IDs) during focal cerebral ischemia are thought to contribute to ischemic damage. Isoflurane and pentobarbital reduce injury (versus the nonanesthetized state) after focal cerebral ischemia. The mechanism by which these drugs reduce injury is not known. This protective effect might be mediated by a reduction in the number of IDs. We measured the frequency of IDs during focal cerebral ischemia in animals anesthetized with isoflurane or pentobarbital and compared it with that in N2O/fentanyl anesthetized animals and in animals in which the N-methyl-D-aspartate receptor antagonist MK801 (dizocilpine) was given. Focal cerebral ischemia was induced by the occlusion of the middle cerebral artery for a period of 2 h. Cortical infarct volumes were determined after 3 h of reperfusion by image analysis of 2,3,5-triphenyl tetrazolium-stained coronal brain sections. The infarct volume was significantly greater in the N2O/fentanyl group than in the other three groups. Infarct volumes in the isoflurane, pentobarbital, and MK801 groups were similar. The frequency of IDs was significantly greater in the N2O/fentanyl group than in the other three groups, and was the least in the MK801 group. There was a direct correlation between the number of IDs and the volume of tissue injury. The data indicate that the protective effect of isoflurane and pentobarbital might, in part, be determined by their ability to reduce IDs during focal ischemia. However, the observation that the infarct volume was similar in the MK801, isoflurane, and pentobarbital groups, despite a greater frequency of IDs in the latter two groups, suggests that mechanisms other than a simple reduction in the number of IDs probably also play a role in anesthetic-mediated cerebral protection.. Transient ischemic depolarizations during focal ischemia contribute to brain injury. Both isoflurane and pentobarbital reduced the frequency of these depolarizations. Isoflurane- and pentobarbital-mediated reduction in the frequency of depolarizations might, in part, mediate the previously documented neuroprotective effect of these drugs.

Topics: Adjuvants, Anesthesia; Anesthetics, Inhalation; Anesthetics, Intravenous; Animals; Cerebral Infarction; Coloring Agents; Dizocilpine Maleate; Electroencephalography; Excitatory Amino Acid Antagonists; Fentanyl; Image Processing, Computer-Assisted; Ischemic Attack, Transient; Isoflurane; Male; Neuroprotective Agents; Nitrous Oxide; Pentobarbital; Rats; Rats, Inbred WKY; Receptors, N-Methyl-D-Aspartate; Reperfusion; Tetrazolium Salts

The response of microglia and astrocytes, as detected immunohistochemically by the monoclonal antibody OX-42 and anti-glial fibrillary acidic protein (GFAP) respectively, was studied in the rat lumbar spinal cord following focal cerebral ischaemia produced by permanent occlusion of the middle cerebral artery (MCA) above the rhinal fissure. At 1 and 2 days after right-sided MCA occlusion, OX-42 immunoreactivity of microglia in both the contralateral dorsal and ventral horns of the lumbar spinal cord was moderately increased compared with cells of the ipsilateral side. The microglial reaction was progressive, with some cells transformed into amoeboid form considered to be macrophages at day 3. By 5 days, many of the reactive microglia, notably in the ventral horn, appeared to encircle the soma of motoneurons. At 7 days, the microglial reaction had subsided while astrocytes in the same area were hypertrophied to replace the perineuronal microglia. The microglial response in both the cerebral cortex and lumbar spinal cord was effectively reduced by the N-methyl-D-aspartate (NMDA) receptor antagonist, MK-801. Present results suggest that following MCA occlusion, the vigorous response of microglia, and subsequently astrocytes, in the spinal cord in extra-focal areas far removed from the primary site of ischaemia may be mediated by glutamate released from the ischaemic corticospinal neurons through NMDA receptors on the postsynaptic spinal cord neurons.

Topics: Animals; Arterial Occlusive Diseases; Astrocytes; Cerebral Arteries; Dizocilpine Maleate; Excitatory Amino Acid Antagonists; Immunohistochemistry; Ischemic Attack, Transient; Lumbosacral Region; Male; Microglia; Rats; Rats, Wistar; Spinal Cord

Both dizocilpine (MK-801) and isoflurane antagonize glutamatergic neurotransmission. In this study, we examined the relative neuroprotective effects of these drugs administered in equianesthetic doses before the onset of focal cerebral ischemia. Rats were anesthetized with 1.0%-1.5% isoflurane and surgically prepared for filament occlusion of the middle cerebral artery (MCAO). After preparation, one group (n = 22) remained anesthetized with 0.7% isoflurane. Another group (n = 18) was given dizocilpine (1 mg/kg intraperitoneally), and isoflurane was discontinued. The third group (n = 18) was allowed to awaken immediately after the onset of ischemia. MCAO persisted for 75 min. Epidural temperature was controlled at 37.5 degrees C during ischemia and the first 22 h of recovery. A 7-day recovery interval was allowed. Total infarction volumes (mean +/- SD) were less for the dizocilpine group (100 +/- 65 mm3) versus the awake group (182 +/- 36 mm3; P = 0.001). Infarction volumes did not differ significantly between the isoflurane group (142 +/- 81 mm3) and either the dizocilpine (P = 0.11) or the awake group (P = 0.15). Isoflurane was examined at doses used clinically but smaller than those found to reduce N-methyl-D-aspartate (NMDA)-mediated injury in vitro. This study supports the hypothesis that NMDA receptor activation is injurious during focal ischemia and that amelioration of focal ischemic brain damage by NMDA receptor antagonists persists under normothermic conditions.. Rats underwent focal cerebral ischemia with rigid maintenance of brain normothermia. The glutamate receptor antagonist dizocilpine was effective in reducing cerebral infarction size during persistent conditions of brain normothermia. In contrast, isoflurane administered at equianesthetic doses did not reduce infarction size. This study supports the hypothesis that N-methyl-D-aspartate receptor activation is injurious during focal ischemia and that amelioration of focal ischemic brain damage by N-methyl-D-aspartate receptor antagonists persists under normothermic conditions.

Topics: Animals; Dizocilpine Maleate; Excitatory Amino Acid Antagonists; Ischemic Attack, Transient; Male; Neuroprotective Agents; Rats; Rats, Wistar; Receptors, N-Methyl-D-Aspartate

1. Excitotoxic and apoptotic mechanisms have been implicated in the pathophysiology of cerebral ischaemia. Both MK-801, an NMDA receptor antagonist, or peptide inhibitors of the caspase family (z-VAD.FMK and z-DEVD.FMK), protect mouse brain from ischaemic cell damage. In this study, we examined whether these drugs which act via distinct mechanisms, afford even greater neuroprotection when given in combination following 2 h MCA occlusion (filament model) and 18 h reperfusion. 2. Given alone as pretreatment, MK-801 (1, 3 and 5 mg kg(-1), but not 0.3 mg kg(-1), i.p.) decreased infarct size by 34-75%. When injected 1 h after occlusion and before reperfusion, 3 mg kg(-1) reduced injury but not when administered I h after reperfusion. 3. Pretreatment with a subthreshold dose of MK-801 (0.3 mg kg(-1)) plus a subthreshold dose of z-VAD.FMK (27 ng) or z-DEVD (80 ng) significantly decreased infarct size by 29 and 30%, respectively, and enhanced neurological function. 4. Administering a subthreshold dose of z-VAD.FMK (27 ng) or z-DEVD.FMK (80 ng) as pretreatment extended the time window for MK-801 (3 mg kg(-1)) by 2 h from 1 h before reperfusion to at least 1 h after reperfusion. 5. Pretreating with a subthreshold dose of MK-801 (0.3 mg kg(-1)) extended the time window for z-DEVD.FMK (480 ng) from 1 h after reperfusion to at least 3 h after reperfusion. 6. We conclude that caspase inhibitors which putatively block apoptotic cell death and inhibit cytokine production and the NMDA antagonist MK-801 act synergistically and prolong their respective therapeutic windows in cerebral ischaemia.

Topics: Animals; Cysteine Proteinase Inhibitors; Dizocilpine Maleate; Dose-Response Relationship, Drug; Drug Synergism; Excitatory Amino Acid Antagonists; Ischemic Attack, Transient; Male; Mice; Receptors, N-Methyl-D-Aspartate; Time Factors

Evoked postsynaptic potentials of CA1 pyramidal neurons in rat hippocampus were studied during 48 h after severe ischemic insult using in vivo intracellular recording and staining techniques. Postischemic CA1 neurons displayed one of three distinct response patterns following contralateral commissural stimulation. At early recirculation times (0-12 h) approximately 50% of neurons exhibited, in addition to the initial excitatory postsynaptic potential, a late depolarizing postsynaptic potential lasting for more than 100 ms. Application of dizocilpine maleate reduced the amplitude of late depolarizing postsynaptic potential by 60%. Other CA1 neurons recorded in this interval failed to develop late depolarizing postsynaptic potentials but showed a modest blunting of initial excitatory postsynaptic potentials (non-late depolarizing postsynaptic potential neuron). The proportion of recorded neurons with late depolarizing postsynaptic potential characteristics increased to more than 70% during 13-24 h after reperfusion. Beyond 24 h reperfusion, approximately 20% of CA neurons exhibited very small excitatory postsynaptic potentials even with maximal stimulus intensity. The slope of the initial excitatory postsynaptic potentials in late depolarizing postsynaptic potential neurons increased to approximately 150% of control values up to 12 h after reperfusion indicating a prolonged enhancement of synaptic transmission. In contrast, the slope of the initial excitatory postsynaptic potentials in non-late depolarizing postsynaptic potential neurons decreased to less than 50% of preischemic values up to 24 h after reperfusion indicating a prolonged depression of synaptic transmission. More late depolarizing postsynaptic potential neurons were located in the medial portion of CA1 zone where neurons are more vulnerable to ischemia whereas more non-late depolarizing postsynaptic potential neurons were located in the lateral portion of CA1 zone where neurons are more resistant to ischemia. The result from the present study suggests that late depolarizing postsynaptic potential and small excitatory postsynaptic potential neurons may be irreversibly injured while non-late depolarizing postsynaptic potential neurons may be those that survive the ischemic insult. Alterations of synaptic transmission may be associated with the pathogenesis of postischemic neuronal injury.

Topics: Animals; Dizocilpine Maleate; Electric Stimulation; Electrophysiology; Evoked Potentials; Excitatory Amino Acid Agonists; Excitatory Postsynaptic Potentials; Ischemic Attack, Transient; Male; Pyramidal Cells; Rats; Rats, Wistar; Reperfusion Injury; Synaptic Transmission

Expression of brain-derived neurotrophic factor (BDNF) may play a role in the mechanism of neuronal cell death after cerebral ischemia. We investigated the changes in levels of mRNAs encoding BDNF and its promoters in the rat brain after transient forebrain ischemia. Transient forebrain ischemia was induced by occlusion of bilateral common carotid arteries and systemic hypotension for 8 min. The alterations in BDNF gene expression in the hippocampus and in the cerebral cortex were examined by in situ hybridization using a mouse BDNF cDNA probe and cDNA probes including exon-specific promoters. BDNF transcripts were rapidly enhanced after the ischemic insult, both in the hippocampus and the cerebral cortex. NBQX suppressed the enhanced gene expression of BDNF markedly in the dentate gyrus (DG). In contrast, MK-801 had little effect on BDNF expression. In the piriform cortex, MK-801 or NBQX reduced the expression only moderately. After the ischemic insult, promoter specific BDNF 5'-exon I and exon III were increased remarkably in the DG. The increase in exon I in DG was suppressed partially by MK-801 and NBQX, while the increase in exon III in CA3 was suppressed by MK-801 but that in DG was not suppressed by either antagonist. In the piriform cortex, exon III was increased remarkably and this increase was not influenced by either agonist. These results suggest that the gene expression of BDNF was enhanced by transient ischemia both in the hippocampus and the cerebral cortex and that the cerebral ischemia stimulated at least two different promoter- and neuron type-specific pathways regulating expression of the BDNF gene mediated by glutamate receptors of non-NMDA type and NMDA type.

Topics: Animals; Brain-Derived Neurotrophic Factor; Cerebral Cortex; Dizocilpine Maleate; DNA Probes; Excitatory Amino Acid Antagonists; Exons; Gene Expression; Hippocampus; In Situ Hybridization; Ischemic Attack, Transient; Male; Mice; Promoter Regions, Genetic; Quinoxalines; Rats; Rats, Wistar; RNA, Messenger; Tissue Distribution

Changes of inositol 1,4,5-trisphosphate receptor (IP3R) mRNA expression after transient brain ischemia and the effect of MK-801, a non-competitive N-methyl-D-aspartic acid (NMDA) receptor antagonist, on the IP3R mRNA expression was studied in mongolian gerbil brain by in situ hybridization. Transient ischemia was induced by ligating left common carotid artery for 10 min, and the animals were allowed recovery from 15 min to 24 h. MK-801 was introduced intraperitoneally 30 min before ischemia. IP3R mRNA expression was decreased in dentate gyrus and hippocampus from 90 min until 24 h after ischemia. MK-801 pretreatment prevented the change of IP3R mRNA expression after ischemia. These results suggest that IP3R mRNA expression in ischemia may be related with NMDA receptor.

Topics: Animals; Brain; Calcium Channels; Dentate Gyrus; Dizocilpine Maleate; Gerbillinae; Hippocampus; In Situ Hybridization; Inositol 1,4,5-Trisphosphate Receptors; Ischemic Attack, Transient; Male; Receptors, Cytoplasmic and Nuclear; Receptors, N-Methyl-D-Aspartate; Reperfusion Injury; RNA, Messenger; Time Factors; Tissue Distribution

Blockade of adenosine receptors can reduce cerebral infarct size in the model of global ischaemia. Using the potent and selective A2A adenosine receptor antagonist, SCH 58261, we assessed whether A2A receptors are involved in the neuronal damage following focal cerebral ischaemia as induced by occluding the left middle cerebral artery. SCH 58261 (0.01 mg/kg either i.p. or i.v.) administered to normotensive rats 10 min after ischaemia markedly reduced cortical infarct volume as measured 24 h later (30% vs controls, p < 0.05). Similar effects were observed when SCH 58261 (0.01 mg/kg, i.p.) was administered to hypertensive rats (28% infarct volume reduction vs controls, p < 0.05). Neuroprotective properties of SCH 58261 administered after ischaemia indicate that blockade of A2A adenosine receptors is a potentially useful biological target for the reduction of brain injury.

Topics: Animals; Cerebral Infarction; Dizocilpine Maleate; Drug Evaluation, Preclinical; Excitatory Amino Acid Antagonists; Ischemic Attack, Transient; Male; Neuroprotective Agents; Purinergic P1 Receptor Antagonists; Pyrimidines; Rats; Rats, Sprague-Dawley; Triazoles

Focal cerebral lesions in the rat brain induced by photothrombosis cause hyperexcitability of the surrounding brain. This can be demonstrated in brain slices taken from animals several days after lesioning, by analysis of field potential responses to paired-pulse stimulation. We now investigated whether and how these remote effects of a cortical lesion can be modified pharmacologically. Application of the NMDA receptor antagonist, MK-801 ((+)-5-methyl-10, 11-dihydro-5H-dibnzo[a,d]cyclohepten-5,10-imine), was shown to block induction of immediate early genes and activation of astrocytes as evidenced by glial fibrillary acidic protein (GFAP) staining in the photothrombosis model. However, MK-801 did not affect the hyperexcitability that had been demonstrated by field potential recordings in brain slices. In another series of experiments, lubeluzole ((+)-(S)-4-(2-benzothiazolylmethylamino)-alpha-[(3,4-difluoroph enoxy) methyl]-1-piperidineethanol), which inhibits the glutamate-activated nitric oxide pathway as evidenced by down-regulation of intracellular cyclic GMP, was given immediately after induction of the insult. This reduced hyperexcitability as investigated 7 days later. In the light of these data one can suggest that a nitric oxide-cyclic GMP-related mechanism may be responsible for functional alterations in the surround of photothrombotic brain lesions.

Topics: Animals; Cerebral Cortex; Dermatitis, Phototoxic; Disease Models, Animal; Dizocilpine Maleate; Electrophysiology; Evoked Potentials; Excitatory Amino Acid Antagonists; Intracranial Embolism and Thrombosis; Ischemic Attack, Transient; Male; Neuroprotective Agents; Piperidines; Rats; Rats, Wistar; Receptors, N-Methyl-D-Aspartate; Thiazoles

Citicoline, a naturally occurring precursor of phosphatidylcholine, is neuroprotective and is currently being assessed in clinical trials. To evaluate potential synergistic neuroprotective effects of prolonged citicoline treatment and early N-methyl-D-aspartate (NMDA) antagonist therapy, suboptimal treatment regimens of citicoline and MK-801 were tested alone and in combination in a rat model of temporary focal ischemia.. Four groups of Sprague-Dawley rats (n = 12 per group) underwent 90 minutes of temporary middle cerebral artery occlusion (MCAO) with the suture model. Animals were randomly and blindly assigned to one of four treatment groups: (1) saline, vehicle; (2) MK-801, 0.5 mg/kg IV bolus at 60 minutes after MCAO followed by saline 1 mL/kg IP daily for 7 days; (3) saline IV at 60 minutes after MCAO followed by citicoline 250 mg/kg IP daily for 7 days; or (4) both MK-801 and citicoline (daily for 7 days) active treatment. Triphenyltetrazolium chloride staining was used to assess postmortem infarct volume. Neurological scores were determined daily.. Premature mortality between days 2 and 4 was 33.3% in group 1, 41.7% in groups 2 and 3, and 25.0% in group 4. Mean corrected infarct volume was significantly reduced in group 4 compared with the others (175.2 +/- 89.3 mm3 in group 1, 179.1 +/- 78.5 mm3 in group 2, 163.9 +/- 73.7 mm3 in group 3, and 84.7 +/- 56.8 mm3 in group 4 [P < .02, ANOVA and P < .05, Scheffé's test for group 1 versus group 4]). Mean infarct volume in animals dying prematurely was significantly (P < .05, Student's t test) larger in group 1 than those surviving for 7 days (247.2 +/- 89.5 versus 139.2 +/- 68.2 mm3), but there was no significant difference in infarct volume in groups 2, 3, and 4 between animals dying prematurely and those surviving for 7 days.. These results demonstrate synergistic neuroprotective effects of citicoline and an NMDA antagonist in temporary experimental focal ischemia.

Topics: Animals; Cerebral Infarction; Cytidine Diphosphate Choline; Dizocilpine Maleate; Drug Synergism; Excitatory Amino Acid Antagonists; Ischemic Attack, Transient; Neuroprotective Agents; Rats; Rats, Sprague-Dawley; Survival Analysis

This study examined the effect of glycine recognition site antagonism (ACEA 1021) on the incidence of spontaneous depolarizations in the penumbra of a focal ischemic lesion. Rats were administered either vehicle (n = 7), ACEA 1021 (n = 7) or dizocilpine (n = 5) and then underwent 90 min middle cerebral artery occlusion. The cortical direct current (DC) potential was recorded. During ischemia, 7 +/- 3 DC shifts occurred in the vehicle group. ACEA 1021 did not reduce this frequency (7 +/- 2 DC shifts) although dizocilpine did (1 +/- 1 DC shifts; p = 0.02). The previously demonstrated neuroprotective property of ACEA 1021 during focal cerebral ischemia cannot be attributed to reduction of spontaneous depolarization in the ischemic penumbra.

Topics: Animals; Dizocilpine Maleate; Excitatory Amino Acid Antagonists; Ischemic Attack, Transient; Male; Membrane Potentials; Neuroprotective Agents; Quinoxalines; Rats; Rats, Wistar; Receptors, Glycine

Repetitive spreading depression (SD) waves, involving depolarization of neurons and astrocytes and up-regulation of glucose consumption, is thought to lower the threshold of neuronal death during and immediately after ischemia. Using rat models for SD and focal ischemia we investigated the expression of cyclooxygenase-1 (COX-1), the constitutive form, and cyclooxygenase-2 (COX-2), the inducible form of a key enzyme in prostaglandin biosynthesis and the target enzymes for nonsteroidal anti-inflammatory drugs. Whereas COX-1 mRNA levels were undetectable and uninducible, COX-2 mRNA and protein levels were rapidly increased in the cortex, especially in layers 2 and 3 after SD and transient focal ischemia. The cortical induction was reduced by MK-801, an N-methyl-D-aspartic acid-receptor antagonist, and by dexamethasone and quinacrine, phospholipase A2 (PLA2) inhibiting compounds. MK-801 acted by blocking SD whereas treatment with PLA2 inhibitors preserved the wave propagation. NBQX, an alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid/kainate-receptor antagonist, did not affect the SD-induced COX-2 expression, whereas COX-inhibitors indomethacin and diclofenac, as well as a NO synthase-inhibitor, NG-nitro-L-arginine methyl ester, tended to enhance the COX-2 mRNA expression. In addition, ischemia induced COX-2 expression in the hippocampal and perifocal striatal neurons and in endothelial cells. Thus, COX-2 is transiently induced after SD and focal ischemia by activation of N-methyl-D-aspartic acid-receptors and PLA2, most prominently in cortical neurons that are at a high risk to die after focal brain ischemia.

Topics: Animals; Cerebral Cortex; Corpus Striatum; Cortical Spreading Depression; Cyclooxygenase 1; Cyclooxygenase 2; Dexamethasone; Dizocilpine Maleate; Endothelium, Vascular; Enzyme Induction; Enzyme Inhibitors; Excitatory Amino Acid Antagonists; Functional Laterality; Hippocampus; Immunohistochemistry; In Situ Hybridization; Ischemic Attack, Transient; Isoenzymes; Male; Membrane Proteins; Neurons; Phospholipases A; Phospholipases A2; Prostaglandin-Endoperoxide Synthases; Quinacrine; Quinoxalines; Rats; Rats, Wistar; Receptors, N-Methyl-D-Aspartate; RNA, Messenger; Transcription, Genetic

We tested the hypothesis that the administration of the competitive N-methyl-D-aspartate (NMDA) receptor antagonist 2R,4R,5S-(2-amino-4,5-(1,2-cyclohexyl)-7-phosphonoheptanoic acid) (NPC 17742) or cis-4-(phosphonomethyl) piperidine-2-carboxylic acid (CGS 19755) or the noncompetitive NMDA receptor antagonist dizocilpine (MK-801), at the appropriate doses, would all have efficacy in decreasing early postischemic brain injury in a feline model of transient focal ischemia.. Prospective, randomized, controlled animal trial.. University research laboratory.. Forty mixed-breed cats.. Halothane-anesthetized cats underwent 90 mins of left middle cerebral artery occlusion plus 4 hrs of reperfusion. At 75 mins of ischemia, control cats received intravenous saline (n = 10). Experimental cats (n = 10 in each group) were treated with NPC 17742 (5 mg/kg bolus and 2.5 mg/kg/hr throughout reperfusion), MK-801 (5 mg/kg intravenous bolus), or CGS 19755 (40 mg/kg intravenous bolus) in a randomized fashion.. Microsphere-determined blood flow to the ipsilateral inferior temporal cortex and caudate nucleus decreased to the same extent during ischemia, and recovered to the same extent during early reperfusion, in the four groups. Triphenyltetrazolium-determined injury volume of the ipsilateral caudate nucleus in cats treated with NPC 17742 (105 +/- 25 [SEM] mm3), MK-801 (97 +/- 22 mm3), and CGS 19755 (97 +/- 13 mm3) was less than in control cats (198 +/- 21 mm3). Hemisphere injury volumes with NPC 17742 (1209 +/- 405 mm3) and MK-801 (1338 +/- 395 mm3) were less than that value in controls (2193 +/- 372 mm3), whereas injury volume with CGS 19755 (1553 +/- 519 mm3) treatment did not attain significance (p < .09).. NMDA receptor activation during reperfusion may contribute to the progression of injury in ischemic border regions after 90 mins of transient focal ischemia in the cat. At the doses chosen, there appear to be no major differences in therapeutic efficacy for competitive and noncompetitive NMDA receptor antagonists.

Topics: Amino Acids; Animals; Brain; Brain Damage, Chronic; Cats; Cerebrovascular Circulation; Dizocilpine Maleate; Excitatory Amino Acid Antagonists; Ischemic Attack, Transient; Male; Neuroprotective Agents; Pipecolic Acids; Prospective Studies; Receptors, N-Methyl-D-Aspartate

The involvement of glutamate in the development of cerebral metabolic disturbances in mature fetuses after transient ischemia was studied using a hippocampal slice model. We investigated the effects of exogenously applied glutamate or glutamate antagonists on the recovery of energy metabolism and protein synthesis rate (PSR) in hippocampal slices of mature guinea pigs after in vitro ischemia. The slices were incubated in a thermostatically controlled flow-through chamber and gassed with carbogen (95% O2/5% CO2). In vitro ischemia was induced by transferring the slices to an aglycemic, artificial cerebrospinal fluid (aCSF) equilibrated with 95% N2/5% CO2. In a first set of experiments slices were exposed to 10 mM glutamate during a 20-40 min period of in vitro ischemia. In a second set slices were incubated in aCSF containing MK-801 (100 microM) or kynurenic acid (0.5 mM) 30 min before, during and 2 h after in vitro ischemia. After a 12 h recovery phase, the concentrations of adenylates in the slices were measured by HPLC after extraction with perchloric acid. PSR was calculated from the rate of incorporation of [14C]leucine into tissue proteins. Neither glutamate nor glutamate antagonists had any effect on the postischemic recovery of energy metabolism and PSR when applied during in vitro ischemia. It is therefore concluded that glutamate does not play a major role in the development of metabolic disturbances in hippocampal slices from mature guinea pig fetuses subjected to transient in vitro ischemia.

Topics: Adenosine Triphosphate; Animals; Dizocilpine Maleate; Energy Metabolism; Excitatory Amino Acid Antagonists; Female; Glutamic Acid; Guinea Pigs; Hippocampus; Ischemic Attack, Transient; Kinetics; Kynurenic Acid; Nerve Tissue Proteins; Pregnancy

We used in situ hybridization to localize the long-term changes in ornithine decarboxylase (ODC) expression after a 90 min occlusion of the middle cerebral artery (MCAO) in the rat. The ODC mRNA was induced in the ipsilateral dentate gyrus (DG) and throughout the ischemic cortex at 12 h and still at 3 days after reperfusion. The induction was blocked by an N-methyl-D-aspartate (NMDA) receptor antagonist suggesting that ODC induction is NMDA receptor-mediated. The long-lasting up-regulation detected in regions where no cellular damage usually occurs, favors the hypothesis that ODC expression does not contribute to neuronal death after stroke.

Topics: Animals; Blotting, Northern; Dizocilpine Maleate; Gene Expression Regulation; In Situ Hybridization; Ischemic Attack, Transient; Male; Neuroprotective Agents; Ornithine Decarboxylase; Rats; Rats, Wistar; Receptors, N-Methyl-D-Aspartate; RNA, Messenger; Time Factors

The present study investigates the role of N-methyl-D-aspartate (NMDA) receptors in a model of transient focal cerebral ischemia in normotensive rats. The left middle cerebral artery and both common carotid arteries were occluded for 60 min. Preliminary studies indicated that this gave reproducible infarctions of the cortex and striatum. These infarctions were the result of severe ischemia followed by complete reperfusion after clamp removal, as showed by striatal tissue Po2 monitoring. Microdialysis indicated that glutamate concentration increased immediately after occlusion and returned to the baseline value 40 min after clamp removal. MK-801 (1 mg kg-1 i.v.), an antagonist of the NMDA glutamatergic receptor, reduced the cortical infarct volume by 29% (p < 0.001) and the striatal infarct volume by 14% (p < 0.05) when given just prior to ischemia, but had no neuroprotective activity when given 30 min after the onset of ischemia. This short therapeutic window for MK-801 suggests that NMDA receptors play only a transient role in reversible focal ischemia in rats.

Topics: Analysis of Variance; Animals; Cerebral Cortex; Cerebral Infarction; Corpus Striatum; Disease Models, Animal; Dizocilpine Maleate; Glutamic Acid; Ischemic Attack, Transient; Male; Microdialysis; Rats; Rats, Sprague-Dawley; Receptors, N-Methyl-D-Aspartate; Reperfusion

Ischemia or hypoxia activates N-methyl-D-aspartate (NMDA) receptors and results in nitric oxide (NO) production. The purpose of this study was to investigate whether an NMDA channel blocker can inhibit NO production during ischemia.. Temporary cerebral ischemia was induced by middle cerebral artery ligation while common carotid arteries were clamped bilaterally for 40 minutes in urethane-anesthetized rats. Extracellular NO concentration in the cortex was recorded through Nafion- and porphyrine-coated carbon fiber electrodes. Ketamine, and NMDA channel blocker, was administered (50 mg/kg) intraperitoneally 15 minutes before the cerebral artery ligation.. During middle cerebral artery ligation, cortical NO was increased to its peak (18.76+/-3.36 nmol/L) in 7 minutes and then declined. The overflow of NO can be antagonized by pretreatment with ketamine, dizocilpine maleate (MK801), or N(G)-nitro-L-arginine methyl ester (L-NAME). Local application of nitroprusside also induced NO production. However, this effect was not antagonized by ketamine.. These findings demonstrated that NO release induced by short-term cerebral ischemia can be attenuated by pretreatment with NMDA antagonists.

Topics: Animals; Arginine; Cerebral Arteries; Cerebral Cortex; Cerebral Infarction; Dizocilpine Maleate; Enzyme Inhibitors; Excitatory Amino Acid Antagonists; Ischemic Attack, Transient; Ketamine; Kinetics; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitric Oxide Synthase; Rats; Rats, Sprague-Dawley; Time Factors

Protein kinase C (PKC) consists of a family of closely related Ca2+/phospholipid-dependent phosphotransferase isozymes, most of which are present in the brain and are differentially activated by second messengers. Calcium-dependent PKC activity may cause neuronal degeneration after ischemic insult. PKC is also involved in trophic-factor signaling, indicating that activity of some PKC subspecies may be beneficial to the injured brain. Therefore, we screened long-term changes in the expression of multiple PKC subspecies after focal brain ischemia. Middle cerebral artery occlusion was produced by using an intraluminal suture for 30 min of 90 min. In in situ hybridization experiments, mRNA levels of PKC alpha, -beta, -gamma, -delta, -epsilon, and -zeta were decreased in the infarct core 4 hr after ischemia and were lost completely 12 hr after ischemia. In areas surrounding the core, PKC delta mRNA was specifically induced 4, 12, and 24 hr after ischemia in the cortex. At 3 and 7 d, the core and a rim around it showed increased mRNA levels of PKC delta. No other subspecies were induced. At 2 d, immunoblotting demonstrated increased levels of PKC delta protein in the perifocal tissue, and immunocytochemistry revealed an increased number of PKC delta-positive neurons in the perifocal cortex. In the core, PKC delta-positive macrophages and endothelial cells were seen. Pretreatment with MK-801, an NMDA antagonist, inhibited cortical PKC delta mRNA induction. The data show that focal brain ischemia induces PKC delta mRNA and protein but not other PKC subspecies through the activation of NMDA receptors and that the upregulation lasts for several days in neurons of the perifocal zone.

Topics: Animals; Brain; Dizocilpine Maleate; Enzyme Induction; Immunohistochemistry; In Situ Hybridization; Ischemic Attack, Transient; Isoenzymes; Male; Protein Kinase C; Protein Kinase C-delta; Rats; Rats, Wistar; RNA, Messenger

The effects of pretreatment with nicardipine (dihydropyridine Ca2+ channel antagonist), Bay K8644 (dihydropyridine Ca2+ channel agonist), and MK-801 (N-methyl-D-aspartate-receptor antagonist) on changes of platelet-activating factor (PAF) concentrations in transient ischemic brain are reported. The tissue concentration of PAF increases significantly in hippocampus, cortex and thalamus by 210%, 169% and 168% of controls without ischemia-reperfusion, respectively after 1 h of reperfusion. Nicardipine (5 mg/kg) reduces the accumulation of PAF, the remaining increases in hippocampus, cortex and thalamus being 151%, 138% and 145% of the controls, respectively. In contrast, Bay K8644 (2.5 mg/kg) enhances the accumulation of PAF, its concentrations in hippocampus, cortex and thalamus being 376%, 233% and 204% of the controls, respectively. The Bay K8644 enhancement in hippocampus is completely inhibited by pretreatment of nicardipine (5 mg/kg). MK-801 (10 mg/kg) reduces the accumulation of PAF, the remaining increases in hippocampus, cortex and thalamus being 152%, 147% and 144% of the controls, respectively. Moreover, brain tissue from animals subjected to the combined pretreatment with nicardipine (5 mg/kg) and MK-301 (10 mg/kg) indicates there is greater inhibition of ischemia-induced PAF increases than with either drug alone. These results indicate that PAF production in the ischemic brain may be regulated by Ca2+ influx through voltage-sensitive Ca2+ channels which are antagonized and agonized by nicardipine and Bay K8644, respectively and receptor-operated Ca2+ channels which are antagonized by MK-801. Because it is known that increases of intracellular Ca2+ in the brain accompany ischemia and early periods of reperfusion and that PAF exhibits neurotoxicity, the present findings support the role of PAF as a mediator in ischemia-induced brain damage at early stages of reperfusion.

Topics: Analysis of Variance; Animals; Body Temperature; Brain; Cerebral Cortex; Dizocilpine Maleate; Female; Gerbillinae; Hippocampus; Ischemic Attack, Transient; Nicardipine; Organ Specificity; Platelet Activating Factor; Reperfusion; Thalamus; Time Factors

The substantia nigra pars reticulata (SNr) receives both inhibitory GABAergic and excitatory glutamatergic afferents from diverse origins. Ischemic injury to the striatum and/or the globus pallidus causes delayed transneuronal death of the SNr neurons, in the course of which neuronal disinhibition induced by loss of GABAergic inputs is supposed to trigger a lethal hypermetabolic process. In the in vivo experiment presented herein, we clarified the role of glutamatergic action via the N-methyl-D-aspartate receptor in this cell death process. Continuous intraventricular infusion (0.5 microliter/h) of the N-methyl-D-aspartate receptor antagonist MK-801 (1000 micrograms/ml), or of saline (control group) was initiated 24 h after 2 h of transient middle cerebral artery (MCA) occlusion in rats, by which massive ischemic injury was produced in the striatopallidal regions. The measured rectal temperature was not significantly altered in the MK-801-infused and in the control rats throughout the time period examined. The rats were killed at 15 days after MCA occlusion. The volume of the focal ischemic infarction of the MK-801-infused group did not significantly differ from that of controls. Also, MK-801-infusion did not significantly ameliorate the nigral atrophy subsequent to MCA occlusion. In association with a marked depletion of GABAergic afferent fibers, neuronal cell number in the ipsilateral SNr was significantly decreased in the control group. In contrast, the neuronal cell loss in the nucleus was completely prevented in the MK-801-infusion group. The data suggested that withdrawal of GABAergic inputs may cause a severe imbalance between excitation and inhibition of the SNr neurons and may eventually result in neurotoxicity mediated by the N-methyl-D-aspartate receptor. Suppression of glutamatergic excitatory effects by suitable drugs may be a reasonable therapy for the transneuronal death of the SNr neurons.

Topics: Animals; Cell Death; Cerebral Ventricles; Corpus Striatum; Dizocilpine Maleate; Excitatory Amino Acid Antagonists; Globus Pallidus; Infusions, Parenteral; Ischemic Attack, Transient; Male; Neurons; Neuroprotective Agents; Rats; Rats, Wistar; Reaction Time; Receptors, N-Methyl-D-Aspartate; Substantia Nigra

Diffusion-weighted MRI has been used to investigate therapeutic intervention with MK-801 in an animal model of permanent focal cerebral ischaemia. The animals were imaged continuously for 4 h and again at 24 h following occlusion of the middle cerebral artery (MCA) allowing the development of the ischaemic lesion to be monitored continuously in the same animals. An increased DWI signal, seen as a region of hyperintensity, was detected 1 h after MCA-occlusion in the lateral cortex and caudate nucleus in both control and MK-801 (administered at a dose of 3 mg/kg i.p. 5 min post-ischaemia) treated animals. However, the volume of hemispheric and cortical hyperintensity was smaller in the MK-801-treated animals. The area of hyperintensity progressively increased in the control group over the 4 h imaging time and there was also an increase in the area of hyperintensity between 4 and 24 h. At these time points the area of hyperintensity encompassed the dorsolateral cortex and caudate nucleus. MK-801 treated animals also demonstrated some progressive increase in the area of hyperintensity between 1 and 3 h, but no significant increase in the area of hyperintensity was seen after this time. The hyperintense regions at 4 and 24 h were restricted to the so-called 'core areas' of the lesion in MK-801-treated animals. Thus, using DWI the tissue 'at risk' following ischaemia could be identified and the protective effect of therapeutic intervention demonstrated.

Topics: Analysis of Variance; Animals; Cerebral Infarction; Diffusion; Disease Models, Animal; Dizocilpine Maleate; Evaluation Studies as Topic; Excitatory Amino Acid Antagonists; Ischemic Attack, Transient; Magnetic Resonance Imaging; Male; Neuroprotective Agents; Rats; Rats, Sprague-Dawley; Receptors, N-Methyl-D-Aspartate

The mechanism of cerebral ischaemic injury is complex and likely involves more than a single pathophysiologic event. Drugs are available which interfere with numerous harmful biochemical and pharmacologic processes begun by ischaemia. Hence, combination chemotherapy might be useful in cerebral ischaemia. The purpose of the present study was to examine the degree of histologic protection against necrosis using a combination of agents which respectively block free radical production (U74006F, tirilazad mesylate), block NMDA receptors (MK-801, dizocilpine maleate), ameliorate hyperglycaemic damage (insulin) and reduce post-ischaemic epileptic damage (diazepam). Each treatment regimen used has been previously individually examined. Fasted rats were divided into four groups receiving either no treatment, the lipid peroxidation inhibitor U74006F, U74006F plus MK-801, or U74006F plus MK-801 plus insulin and diazepam. One week following ten minutes of transient forebrain ischaemia, quantitative neuropathology was done in all brain regions demonstrating necrosis. The neocortex showed a trend toward a progressively increasing benefit with the addition of U74006F, MK-801, insulin and diazepam, but no clear trends were apparent in hippocampus, striatum, or other brain regions. The findings demonstrate that the cerebral cortex, a tissue of major importance damaged in cerebral ischaemia, can be salvaged in fasted animals with the presently used combination chemotherapeutic regimen, but also illustrate the need to search for combination chemotherapeutic regimens which may be more effective in other brain regions for the metabolic protection of brain tissue against cerebral ischaemia.

Topics: Animals; Blood Gas Analysis; Blood Glucose; Body Temperature; Cerebral Cortex; Diazepam; Dizocilpine Maleate; Drug Therapy, Combination; Hydrogen-Ion Concentration; Insulin; Ischemic Attack, Transient; Male; Pregnatrienes; Prosencephalon; Rats; Rats, Wistar

This study investigated astroglial responses after focal cerebral ischemia in the rat cortex induced by photothrombosis. Astrocyte activation was studied at various time points by immunocytochemistry for glial fibrillary acidic protein (GFAP) and vimentin (VIM). We found a dual astrocytic response to focal ischemia: In the border zone of the infarct, GFAP-positive astrocytes were present within 2 days and persisted for 10 weeks. These astrocytes additionally expressed VIM. Remote from the ischemic lesion, cortical astrocytes of the entire ipsilateral hemisphere transiently expressed GFAP, but not VIM, beginning on day 3 after photothrombosis. This response had disappeared on day 14. By recording DC potentials, five to seven spreading depressions (SD) could be detected on the cortical surface during the first 2 h after photothrombosis. Treatment with MK801, a non-competitive NMDA-receptor antagonist, completely abolished SD and remote ipsilateral astrocytic activation, while the reaction in the border zone of the infarct remained unchanged. Functionally, persistent astrocytosis around the infarct might be induced by leukocyte-derived cytokines, while NMDA-receptor-mediated SD might cause remote responses.

Topics: Animals; Astrocytes; Cerebral Cortex; Cortical Spreading Depression; Dizocilpine Maleate; Glial Fibrillary Acidic Protein; Ischemic Attack, Transient; Male; Neuroprotective Agents; Photic Stimulation; Potassium Chloride; Rats; Rats, Wistar; Stimulation, Chemical; Thrombosis; Vimentin

1. Changes in the peripheral type benzodiazepine binding site density following middle cerebral artery occlusion in the mouse, have been used as a marker of neuronal damage. These sites can be identified using the selective ligand [3H]-PK 11195 located on non neuronal cells, macrophages and astroglia, within the CNS. Glial cell proliferation and macrophage invasion is an unvoidable sequelae to cerebral ischaemic injury, secondary to neuronal loss. Following occlusion of the left middle cerebral artery (left MCA) a reproducible lesion was found in the parietal cortex within 7 days which gave rise to a significant increase in [3H]-PK 11195 binding. 2. Treatment of animals with the sodium channel blocker, lifarizine, significantly reduced the ischaemia-induced increase in [3H]-PK 11195 binding when given either 30 min pre-ischaemia and three times daily for 7 days at 0.5 mg kg-1, i.p. (P < 0.01) or delayed until 15 min post-ischaemia and three times daily for 7 days at 0.5 mg kg-1, i.p. (P < 0.001). Lifarizine was an effective neuroprotective agent in this model of focal ischaemia in the mouse. 3. Lifarizine also showed a dose-related protection against the ischaemia-induced increase in [3H]-PK 11195 binding with significant protection at doses of 0.1 mg kg-1, i.p. (P < 0.05), 0.25 mg kg-1, i.p. (P < 0.01) or 0.5 mg kg-1, i.p. (P < 0.01) 15 min post-ischaemia and b.i.d. for 7 days. No significant change is seen in the Kd for [3H]-PK 11195. The first dose could be delayed for up to 4 h after cerebralartery cauterization and protection was maintained.4. Phenytoin (28 mg kg-1, i.v. 15 min and 24 h post-ischaemia) was also neuroprotective in this model(P<0.01). This agent is thought to interact with voltage-dependent sodium channels to effect its anticonvulsantactions and this mechanism may also underlie its neuroprotective actions in focal cerebralischaemia.5. Agents with other mechanisms of action were also shown to have significant neuroprotection in this model. The non-competitive NMDA antagonist, MK 801, showed significant neuroprotection in the model when given at 0.5 mg kg-1, i.p. 30 min pre-ischaemia with t.i.d. dosing for 7 days (P< 0.001). The dihydropyridine calcium antagonist, nimodipine was not protective when given using the same dosing protocol as MK 801, 0.5 mg kg-1 30 min pre-occlusion and three times daily for 7 days but showed significant protection when given at 0.05 mg kg-1 15 min post-ischaemia and three times daily for 7days. The lipid per

Topics: Animals; Cerebral Cortex; Disease Models, Animal; Dizocilpine Maleate; Dose-Response Relationship, Drug; Imidazoles; Injections, Intraperitoneal; Ischemic Attack, Transient; Isoquinolines; Mice; Neuroprotective Agents; Nimodipine; Phenytoin; Piperazines; Pregnatrienes; Sodium Channels

1. We have recently developed a new model of transient focal ischaemia in the rat utilising topical application of endothelin-1 to the left middle cerebral artery (MCA). In order to validate this approach the present study assessed the neuroprotective efficacy of the NMDA receptor antagonist dizocilpine (MK-801) in the endothelin-1 model. The anti-ischaemic efficacy of the nitric oxide (NO) synthase inhibitor NG-nitro-L-arginine methyl ester (L-NAME) was subsequently evaluated, and contrasted with its efficacy against permanent focal ischaemia, to determine the utility of the endothelin-1 model for identification of novel pharmacoprotective agents. 2. MK-801 (0.12 mg kg-1 bolus, 108 micrograms kg-1 h-1 infusion i.v., either 1 or 2.5 h pre-transient MCA occlusion (MCAO)) induced hypotension that persisted for approximately 1.5 h so that mean arterial blood pressure (MABP) at the time of MCAO was significantly lower in the 1 h group compared with control (MABP: 86 +/- 11, 68 +/- 6 and 84 +/- 4 mmHg (mean +/- s.d.) for saline, 1 h MK-801 and 2.5 h MK-801 groups respectively). The 2.5 h pretreatment schedule resulted in significant reduction (71%) in the volume of hemispheric damage (assessed 4 h post onset of ischaemia) while the 1 h pretreatment schedule did not (volumes of hemispheric damage: 59 +/- 38, 51 +/- 51 and 17 +/- 28 mm3 for saline, 1 h and 2.5 h MK-801 groups). 3. Thus the considerable neuroprotective effect of MK-801 in the endothelin-1 model of transient focal cerebral ischaemia was highly sensitive to drug-induced hypotension. This result is in contrast to previous studies of permanent MCAO where MK-801-induced hypotension did not compromise its neuroprotective action.4. L-NAME (3 mg kg-1, i.v. 30 min pre-MCAO) moderately, but significantly, reduced (16%) the volume of ischaemic damage 4 h post-permanent MCA occlusion, whereas the 29% reduction in volume of damage achieved in the model of transient focal ischaemia did not attain significance due to the greater variability associated with this model. L-NAME did not significantly alter MABP in either model.5. The modest neuroprotection achieved with NO synthase inhibition suggests NO is of relatively minor importance as a mediator of neurotoxicity following permanent focal cerebral ischaemia. In addition the comparable efficacy of L-NAME against transient focal ischaemia suggests the presence of reperfusion does not enhance the contribution of NO to neuronal injury in the acute (4 h) phase foll

Topics: Amino Acid Oxidoreductases; Animals; Arginine; Blood Pressure; Brain; Brain Ischemia; Cerebral Arteries; Dizocilpine Maleate; Endothelins; Ischemic Attack, Transient; Male; NG-Nitroarginine Methyl Ester; Nitric Oxide Synthase; Rats; Rats, Sprague-Dawley; Receptors, N-Methyl-D-Aspartate

Topics: Amino Acid Oxidoreductases; Analysis of Variance; Animals; Arginine; Cerebral Infarction; Dizocilpine Maleate; Ischemic Attack, Transient; Male; Mice; Molsidomine; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitric Oxide Synthase; Vasodilator Agents

We investigated the postischemic alterations in [3H]MK-801, [3H]muscimol, and [3H]naloxone binding in the gerbil brain, and examined the effect of pentobarbital against these alterations. [3H]MK-801, [3H]muscimol, and [3H]naloxone were used to label N-methyl-D-aspartate (NMDA), gamma-aminobutyric acidA (GABAA), and opiate receptors, respectively. Transient cerebral ischemia was induced for 10 min, and pentobarbital (40 mg/kg) was administered intraperitoneally 30 min before ischemia. Five hours after ischemia, no conspicuous alteration in [3H]MK-801, [3H]muscimol, and [3H]naloxone binding was found in the striatum and hippocampus. Seven days after ischemia, [3H]MK-801 and [3H]naloxone binding was significantly decreased in the striatum and hippocampal area where histological neuronal damage was noted. By contrast, no significant change in [3H]muscimol binding was seen in the above regions except for the hippocampal CA3 sector. The treatment of pentobarbital caused a significant alteration in the binding of [3H]naloxone and [3H]muscimol in various brain areas 5 h after ischemia. However, this drug showed no significant change in [3H]MK-801 binding in the brain. Seven days after ischemia, pentobarbital partly ameliorated a significant reduction in [3H]MK-801 and [3H]naloxone binding in the striatum and hippocampus. A histological study also showed that pentobarbital afforded neuronal protection against the damage to the brain except for the hippocampal CA1 sector 7 days after ischemia. These results suggest that NMDA and opiate receptors are damaged after ischemia, whereas GABAA receptors are unaffected. They also demonstrate that opiate receptors are severe affected by the treatment of pentobarbital, compared with NMDA and GABAA receptors. These findings are of interest in relation to the mechanism of ischemic neuronal damage.

Topics: Animals; Brain; Dizocilpine Maleate; Gerbillinae; Ischemic Attack, Transient; Male; Muscimol; Naloxone; Pentobarbital; Radioligand Assay

The expression of c-fos protein was examined by means of immunocytochemistry in the rat brain following incomplete ischaemia, to elucidate the molecular mechanisms of post-ischaemic neuronal death and of the modulated neurotransmission of surviving neurons. Incomplete ischaemia was produced by permanent unilateral or bilateral common carotid artery (CCA) occlusion. After 1 h of unilateral occlusion, the level of c-fos protein-like nuclear immunoreactivity increased in cortical neurons ipsilateral to the insult, especially in cingulate and piriform cortices. The reactivity peaked at 3-6 h, and was undetectable after 3 days. A number of scattered immunostained neurons in the ipsilateral subiculum, CA 1 and dentate gyrus became visible after 1 day. The effect reached a peak between 1-3 days, then returned to basal levels by 7 days. Bilateral CCA occlusion showed a similar distribution of immunoreactivity, but on both hemispheres. Immunoreactive neurons were more numerous and intensely stained but more transient. The induction of c-fos was completely blocked or reduced by treatment with MK-801. Our results suggest that c-fos expression after CCA occlusion is NMDA receptor mediated, and that it has a specific role in neurons after ischaemic insult.

Topics: Animals; Brain; Carotid Artery, Common; Dizocilpine Maleate; Ischemic Attack, Transient; Ligation; Male; Proto-Oncogene Proteins c-fos; Rats; Receptors, N-Methyl-D-Aspartate

Several reports have indicated that the two glutamate receptor antagonists, dizocilpine (that binds to the phencyclidine recognition site of the NMDA (N-methyl-D-aspartate) receptor) and NBQX (2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo(F)quinoxaline, that binds to the AMPA (alpha-amino-3-hydroxy-5-methyl-isoxazole) receptor), protect neurons against damage caused by hypoxia, ischemia or excitotoxicity. We, therefore, used a combination of these drugs to achieve enhanced neuroprotection. Primary cultures of rat hippocampal neurons were challenged by glutamate intoxication. Both dizocilpine and NBQX produced dose-dependent increases in the percentage of viable neurons. Combined treatment with both glutamate receptor antagonists had an over-additive neuroprotective effect. Simultaneous administration of dizocilpine and NBQX also had a pronounced neuroprotective effect in vivo in mice subjected to focal cerebral ischemia and rats with global forebrain ischemia. This suggest that such a combination may have therapeutic relevance.

Topics: Animals; Brain Ischemia; Cells, Cultured; Dizocilpine Maleate; Drug Synergism; Glutamates; Glutamic Acid; Hippocampus; Ischemic Attack, Transient; Male; Mice; Neurons; Quinoxalines; Rats; Rats, Inbred F344; Rats, Wistar; Receptors, AMPA

There is strong evidence to implicate glutamate in the cerebral damage caused by ischemia. In this study we investigated the role of glutamate receptors in mediating effects of middle cerebral artery occlusion (MCAO) on immediate early gene expression in the rat by quantitation of mRNA levels.. The effect of MCAO on the induction of immediate early genes was studied in five regions, both ipsilateral and contralateral to the occlusion: the "core" ischemic area of the cortex in the central region of the middle cerebral artery territory, the surrounding area, frontal cortex, occipital cortex, and hippocampus. Levels of c-fos, c-jun, zif-268, and krox-20 mRNA were measured by Northern and slot blot analysis.. A large induction of c-fos mRNA was obtained in all four cortical regions ipsilateral to the occlusion, with the greatest effect detected in the core area. Little effect was detected in the ipsilateral hippocampus and in all contralateral regions. Pretreatment with MK-801 (3 mg/kg) largely inhibited the induction of c-fos mRNA, indicating that the induction was mediated through an N-methyl-D-aspartate subtype of glutamate receptor. MCAO also produced a significant induction of c-jun and zif-268 mRNA in ipsilateral cortical regions.. These results indicate that MCAO causes a profound modulation of the expression of multiple genes in an extensive area of cerebral cortex extending beyond the immediate area supplied by the middle cerebral artery. The marked effect of MK-801 indicates the potential importance of glutamate antagonists in restricting the widespread deleterious effects of glutamate.

Topics: Animals; Blood Pressure; Brain; Dizocilpine Maleate; Functional Laterality; Gene Expression; Genes, fos; Genes, Immediate-Early; Genes, jun; Ischemic Attack, Transient; Male; Organ Specificity; Proto-Oncogene Proteins c-fos; Proto-Oncogene Proteins c-jun; Rats; Rats, Sprague-Dawley; RNA, Messenger; Tubulin

Blood-brain barrier permeability alteration, vasogenic brain edema, and infarction, which are more extensive after 3 hours of temporary middle cerebral artery occlusion (MCAO) and 3 hours of reperfusion than after 6 hours of permanent MCAO, develop in rats after prolonged focal cerebral ischemia. Protective effects of excitatory amino acid receptor antagonists have been previously demonstrated after temporary global ischemia and permanent focal ischemia in rats. The purpose of this study was to evaluate the effectiveness of MK-801, a noncompetitive N-methyl-D-aspartate receptor antagonist, in temporary middle cerebral artery occlusion in rats maintained at physiological levels of brain temperature. Rats were anesthetized with chloral hydrate (350 mg/kg, intraperitoneally). The MCAO of rats was occluded by cannulation with a nylon suture for 3 hours, followed by 3 hours of reperfusion accomplished by withdrawing the suture. MK-801 (1 mg/kg, intravenously) or saline (S) was injected immediately before the onset of MCAO. Water content (MK-801, n = 6; S, n = 6), Evans blue dye extravasation (MK-801, n = 6; S, n = 6), infarct volume (MK-801, n = 10; S, n = 10), histology (MK-801, n = 6; S, n = 6), and neurological deficit (MK-801, n = 15; S, n = 18) were measured at the end of 3 hours of reperfusion. Brain temperature was monitored during the experiment. The infarction area (measured by 2, 3, 5-triphenyltetrazolium chloride staining) was reduced (P < 0.001) in the MK-801-treated rats, as was the infarct volume and the severity of neuronal damage (P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Basal Ganglia; Blood-Brain Barrier; Cerebral Cortex; Cerebral Infarction; Dizocilpine Maleate; Ischemic Attack, Transient; Male; Neurologic Examination; Rats; Rats, Sprague-Dawley; Receptors, N-Methyl-D-Aspartate

The selective alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) antagonist 2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo(f)quinoxaline (NBQX) and the selective N-methyl-D-aspartate (NMDA) receptor antagonists MK 801 and ifenprodil were administered to Mongolian gerbils following a 5 min period of bilateral carotid artery occlusion. NBQX when given 4, 6 or 24 h after ischaemia gave a reduced loss of hippocampal CA1 neurones compared to control animals receiving vehicle only. Dizocilipine (MK 801) (1-10 mg/kg i.p.) and ifenprodil (a total of 45 mg/kg i.p.) gave no protection. The peak levels of NBQX obtained in the cerebrospinal fluid of gerbils receiving the neuroprotective dose (3 x 30 mg/kg i.p.) was 1 microM. In gerbil cortex slices, this concentration had no effect on NMDA-evoked depolarization, but had a moderate effect on kainate and gave a total blockade of AMPA depolarizations. It is concluded that antagonists of non-NMDA glutamate receptor subtypes, possibly AMPA, may be a useful therapeutic approach for cerebral ischaemia-related brain damage following global ischaemia.

Topics: alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; Animals; Cerebral Cortex; Dizocilpine Maleate; Excitatory Amino Acid Antagonists; Female; Gerbillinae; Hippocampus; Ibotenic Acid; Ischemic Attack, Transient; Kinetics; Male; Neurons; Piperidines; Quinoxalines; Receptors, AMPA; Receptors, Glutamate; Receptors, N-Methyl-D-Aspartate

The neuroprotective effects of 2,3-dihydroxy-6-nitro-7- sulfamoylbenzo(f)quinoxaline (NBQX), GYKI 52466, and MK-801 were tested following severe forebrain ischemia. Wistar rats were subjected to 10 min of normothermic ischemia and reperfused for 7 days. Necrotic hippocampal CA1 neurons were counted and expressed as a percentage (mean +/- SD). In Experiment 1, saline-treated rats sustained 81 +/- 20% damage to dorsal CA1. Rats given NBQX 30 mg/kg i.p. x3 lost 21 +/- 27% (p < 0.01). Neither MK-801 1 mg i.p. x3 alone, nor in combination with the cytoprotective dose of NBQX protected CA1, with 83 +/- 18 and 54 +/- 34% damage, respectively (NS). Giving NBQX 90 mg/kg i.v. did not protect cells (94 +/- 5%) and resulted in nephrotoxicity. In Experiment 2, rats were given saline or three doses of NBQX 30 mg/kg i.p. immediately at reperfusion (RP) or after a 6-, 12-, or 24-h delay. Saline-treated rats suffered 79 +/- 16% injury. NBQX given immediately resulted in 17 +/- 17% injury, and even if treatment was delayed by either 6 or 12 h, there was marked protection with only 27 +/- 32 and 25 +/- 17% injury, respectively (all p < 0.01). Delaying the initiation of treatment to 24 h was not successful, resulting in 50 +/- 28% injury (NS). In Experiment 3, saline-treated rats lost 81 +/- 19% of CA1 cells, while those given GYKI 52466 10 mg/kg i.p. x5 starting immediately following RP lost 80 +/- 14%.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; Animals; Anti-Anxiety Agents; Benzodiazepines; Brain Diseases; Dizocilpine Maleate; Hippocampus; Ischemic Attack, Transient; Male; Neurons; Prosencephalon; Quinoxalines; Rats; Rats, Wistar

The neuroprotective effects of the platelet-activating factor (PAF) antagonists BN 52020 and BN 52021 were determined in a temperature-controlled model of transient forebrain ischemia in the rat (occlusion of both common carotid arteries combined with lowering of the mean arterial blood pressure to 40 mm Hg for 10 min). After 7 days of recirculation, the ischemic neuronal damage was evaluated histologically within the hippocampus and neocortex. Combined pre- and post-treatment with the PAF antagonists (2 x 25 mg/kg, s.c.) significantly reduced the resulting neuronal damage of the CA1 and CA3 hippocampal subfields and of the occipital and parietal cerebral cortex. The two PAF antagonists were also tested for their neuroprotective activity in primary neuronal cultures isolated from embryonic chick telencephalon. Since an excessive activation of excitatory amino acid receptors is discussed to be of importance for the ischemic brain damage, the cultured neurons were exposed to the excitatory amino acid L-glutamate (1 mM) for a period of 60 min. Twenty hours after the excitotoxic insult, BN 52020- and BN 52021-treated cultures (1-100 microM) showed both a better preserved morphology, as well as a dose-dependent increase in cell viability and protein content compared to the control cultures. Our results demonstrate that the PAF antagonists BN 52020 and BN 52021 have the capacity to protect brain tissue against ischemic neuronal damage independent of hypothermic effects and are also capable of reducing excitotoxic damage of telencephalic neurons from chick embryos cultured in the absence of glial or endothelial cells. We thus propose that PAF plays an important role in the pathophysiology of ischemic/excitotoxic neuronal injury via a direct action on neurons.

Topics: Animals; Cells, Cultured; Cerebral Cortex; Chick Embryo; Diterpenes; Dizocilpine Maleate; Excitatory Amino Acid Antagonists; Ginkgolides; Glutamates; Glutamic Acid; Hippocampus; Ischemic Attack, Transient; Lactones; Male; Neurons; Platelet Activating Factor; Rats; Rats, Wistar; Telencephalon

Calcium influx is believed to play a critical role in the cascade of biochemical events leading to neuronal cell death in a variety of pathological settings, including cerebral ischemia. The synthetic omega-conotoxin peptide SNX-111, which selectively blocks depolarization-induced calcium fluxes through neuronal N-type voltage-sensitive calcium channels, protected the pyramidal neurons in the CA1 subfield of the hippocampus from damage caused by transient forebrain ischemia in the rat model of four-vessel occlusion. SNX-111 provided neuroprotection when a single bolus injection was administered intravenously up to 24 hr after the ischemic insult. These results suggest that the window of opportunity for therapeutic intervention after cerebral ischemia may be much longer than previously thought and point to the potential use of omega-conopeptides and their derivatives in the prevention or reduction of neuronal damage resulting from ischemic episodes due to cardiac arrest, head trauma, or stroke. Microdialysis studies showed that SNX-111 was 3 orders of magnitude less potent in blocking potassium-induced glutamate release in the hippocampus than the conopeptide SNX-230, which, in contrast to SNX-111, failed to show any efficacy in the four-vessel occlusion model of ischemia. These results imply that the ability of a conopeptide to block excitatory amino acid release does not correlate with its neuroprotective efficacy.

Topics: Animals; Calcium Channels; Dizocilpine Maleate; Dose-Response Relationship, Drug; Drug Administration Schedule; Glutamates; Glutamic Acid; Hippocampus; Ischemic Attack, Transient; Male; Neurons; omega-Conotoxins; Peptides; Potassium; Prosencephalon; Pyramidal Tracts; Rats; Rats, Inbred F344; Reperfusion; Time Factors

We performed receptor autoradiography to determine sequential changes in the binding of N-methyl-D-aspartate (NMDA) and gamma-aminobutyric acidA (GABAA) 1 h to 1 month after 10 min of transient cerebral ischemia in the gerbil. [3H]MK-801 and [3H]muscimol were used to label NMDA and GABAA receptors, respectively. [3H]MK-801 binding showed no significant changes in the striatum and hippocampus at an early stage (1-24 h) after ischemia. Thereafter, [3H]MK-801 binding exhibited a significant reduction in the dorsolateral striatum, most of hippocampal CA1 sector and dentate gyrus 48 h or 7 days of recirculation. However, [3H]MK-801 binding progressively depressed in the hippocampal CA1 sector 1 month after ischemia, whereas other regions showed no significant alteration in the binding. By contrast, [3H]muscimol binding was unchanged in all brain areas throughout the recirculation period. A histological study also demonstrated that transient ischemia caused severe neuronal damage in the striatum and hippocampus. These results demonstrate that NMDA and GABAA receptors are relatively resistant to severe degenerative processes. Furthermore, our finding suggests that transient ischemia may induce long-term changes in the properties of survival neurons or interneurons especially in the hippocampal CA1 sector.

Topics: Animals; Autoradiography; Brain Chemistry; Dizocilpine Maleate; gamma-Aminobutyric Acid; Gerbillinae; Glutamates; Glutamic Acid; Histocytochemistry; Ischemic Attack, Transient; Male; Muscimol; N-Methylaspartate; Neurotransmitter Agents; Receptors, GABA; Receptors, N-Methyl-D-Aspartate

To examine the role of calcium influx in the early phase after brief forebrain ischemia and subsequent delayed neuronal cell death in the hippocampus, 45Ca autoradiography and electron microscopic cytochemistry, by a combined oxalate-pyroantimonate method, were carried out in gerbil brains after 5 min bilateral common carotid arterial occlusion. Further, neuronal damage during the ischemic and postischemic periods was determined by conventional or immunohistochemical staining for microtubule-associated protein 2 (MAP2) with and without calcium-entry blockers. 45Ca autoradiography showed a high peak of calcium in the hippocampus at 5 min of recirculation. Electron cytochemical microscopy also demonstrated accumulation of intracellular calcium pyroantimonate deposits in the neuronal cells in all regions. At 30 min of reperfusion, amounts of calcium in the hippocampus returned to the control levels, and intracellular dense calcium pyroantimonate deposits were reduced in these areas. Loss of the reaction for MAP2 was noted in the medial CA1 of the hippocampus immediately after 5 min ischemia and at 5 and 30 min after reperfusion. MK-801 (10 mg kg-1), an N-methyl-D-aspartate (NMDA) receptor antagonist, injected intraperitoneally 1 h before ischemia, suppressed the early increase of calcium in the forebrain and neuronal cell necrosis in the CA1. However, neither injection of MK-801 30 min after reperfusion nor preischemic treatment with 0.5 mg kg-1 Nimodipine or 1 mg kg-1 Nicardipine, voltage-sensitive calcium channel antagonists, prevented neuronal death. In immunohistochemical staining for MAP2, the ischemic lesion in the medial CA1 maintained after 5 min ischemia and the subsequent early reperfusion period in the untreated brains was protected by the preischemic injection of 10 mg kg-1 MK-801, but was not restored by the injection of 0.5 mg kg-1 Nimodipine or 1 mg kg-1 Nicardipine. In conclusion, it is suggested that an early excess of calcium influx could be caused mainly by excitatory amino acid overload through NMDA receptor-mediated calcium channels during the ischemic and early postischemic periods.

Topics: Animals; Autoradiography; Brain; Calcium; Calcium Channel Blockers; Calcium Radioisotopes; Cell Death; Choroid Plexus; Dizocilpine Maleate; Female; Gerbillinae; Hippocampus; Ischemic Attack, Transient; Kinetics; Male; Microscopy, Electron; Microtubule-Associated Proteins; Necrosis; Neurons; Nicardipine; Nimodipine; Organ Specificity; Parietal Lobe; Prosencephalon; Pyramidal Cells; Reference Values; Thalamus

Five minutes of oxygen and glucose deprivation (termed "in vitro ischemia") causes long-term synaptic transmission failure (LTF) in the CA1 region of the rat hippocampal slice. Dependence of LTF on cell calcium was tested by generating graded reductions in cell Ca. There was a strong correlation between the average level of exchangeable cell Ca in CA1 during ischemia, and the extent of LTF. In standard buffer, exchangeable cell Ca in CA1 increased by 35% after 3 min of ischemia and remained elevated for the entire 5 min of ischemia. Unidirectional Ca influx increased by 35% during the first 2.5 min of ischemia and remained at that level for the next 2.5 min. There were no changes in unidirectional Ca efflux during this period. Thus, the accumulation results from increased influx of Ca. Ca influx during the first 2.5 min of ischemia depended entirely on NMDA channels; it was completely blocked by the noncompetitive NMDA receptor antagonist MK-801. However MK-801 had no effect during the second 2.5 min. This inactivation of NMDA-mediated influx during ischemia appears to result from dephosphorylation. Okadaic acid increased Ca influx during the second 2.5 min of ischemia and this increase was blocked by MK-801. The ischemia-induced Ca influx during the second 2.5 min of ischemia was attenuated 25% by nifedipine (50 microM) and an additional 35% by the Na/Ca exchange inhibitor benzamil (100 microM). The AMPA/kainate antagonist DNQX had no effect on the Ca influx. Antagonists were used to relate Ca influx to LTF. Blockade of enhanced Ca entry during ischemia in standard buffer (2.4 mM Ca) had no effect on LTF, consistent with total cell Ca prior to ischemia being adequate to cause complete LTF. However, MK-801 strongly protected against LTF when the buffer contained 1.2 mM Ca, a more physiological level. MK-801 combined with DNQX prevented transmission damage in standard buffer. Thus, AMPA/kainate receptor activation contributes to ischemic damage, although not by enhancing Ca entry.

Topics: Amiloride; Animals; Calcium; Dizocilpine Maleate; Ethers, Cyclic; Guanidines; Hippocampus; In Vitro Techniques; Ischemic Attack, Transient; Kinetics; Male; Microscopy, Electron; Okadaic Acid; Pyramidal Tracts; Quinoxalines; Rats; Rats, Sprague-Dawley; Time Factors

The present study shows that systemic administration of the selective, non-competitive N-methyl-D-aspartate antagonist MK-801 [(+)-5-methyl-10,11-dihydroxy-5H-dibenzo (a,d)-cyclohepten-5,10-imine] dose-dependently induces ipsiversive rotational behavior in the rats with a unilateral striatal lesion produced by transient middle cerebral artery occlusion or in those with a unilateral nigrostriatal lesion produced by 6-hydroxydopamaine. In relation to a functional model of the basal ganglia-thalamocortical 'motor' circuit, the present data suggest that the striatum may be one of the most important sites where MK-801 acts in the basal ganglia, with its being responsible for the circling behavior of the animal models.

Topics: Animals; Dizocilpine Maleate; Dose-Response Relationship, Drug; Ischemic Attack, Transient; Motor Activity; Neostriatum; Oxidopamine; Rats; Receptors, N-Methyl-D-Aspartate; Stereotyped Behavior; Substantia Nigra

Mongolian gerbils were subjected to transient forebrain ischaemia by occluding both common carotid arteries for 7 min. Subcutaneous administration of either the kappa-opioid receptor agonist enadoline (CI-977; 1 mg kg-1), or the non-competitive NMDA receptor antagonist dizocilpine (MK-801; 3 mg kg-1), at induction of ischaemia prevented neurodegeneration of CA1-CA2 pyramidal neurones in the dorsal hippocampus. It was shown by continuously monitoring intrahippocampal temperature that brain temperature drops by approximately 4 degrees C during ischaemia, when rectal temperature is maintained normothermic. Enadoline at no time point tested affected brain temperature, whereas dizocilpine statistically lowered brain temperature following ischaemia. These findings suggest that enadoline affords neuroprotection in the absence of any hypothermic episode, whilst in the case of dizocilpine, the small transient hypothermia observed following ischaemia may act synergistically or additively with the drug to yield neuroprotection.

Topics: Animals; Benzofurans; Body Temperature; Brain; Dizocilpine Maleate; Female; Gerbillinae; Ischemic Attack, Transient; Models, Biological; Pyrrolidines

Transient forebrain ischemia was produced in gerbils by short-term occlusion of the common carotid arteries under halothane anesthesia. Histological analysis of brains 7 days post-ischemia demonstrated characteristic destruction of CA1 pyramidal cells. lambda Opiate binding (measured with [3H]naloxone in the presence of 300 nM diprenorphine) at 7 days post-ischemia was significantly increased in the stratum lucidum of the hippocampus (the mossy fiber layer), but not in any other region measured, including other hippocampal regions, cortex, amygdala, caudate putamen, thalamus, and hypothalamus. The increase in mossy fiber lambda binding was slow to develop (no increase detected up to 48 h post-ischemia), and long-lasting (binding remained elevated at 32 days post-ischemia). While MK-801 significantly inhibited CA1 pyramidal cell destruction when administered 20 min prior to ischemia, the increase in mossy fiber lambda binding was still evident. None of seven different opioid agonists and antagonists examined had an effect on either the pyramidal cell damage or increased mossy fiber lambda binding seen 7 days after ischemia.

Topics: Afferent Pathways; Animals; Dizocilpine Maleate; Female; Gerbillinae; Hippocampus; Ischemic Attack, Transient; Naloxone; Nerve Fibers; Neurons; Prosencephalon

We investigated the neuroprotective potential of MK-801 (dizocilpine), a noncompetitive N-methyl-D-aspartate (NMDA) antagonist, in the setting of three 5-min periods of global cerebral ischemia separated by 1-h intervals in halothane-anesthetized rats. Each ischemic insult was produced by bilateral carotid artery occlusions plus hypotension (50 mm Hg). Brain temperature was maintained at normothermic levels (36.5-37.0 degrees C) throughout the experiment. MK-801 (3 mg/kg) (n = 6) or saline (n = 6) was injected intraperitoneally 45 min following the end of the first ischemic insult. Following 7-day survival, quantitative neuronal counts of perfusion-fixed brains revealed severe ischemic damage in hippocampal CA1 area, neocortex, ventrolateral thalamus, and striatum of untreated rats. By contrast, significant protection was observed in MK-801-treated rats. In area CA1 of the hippocampus, numbers of normal neurons were increased 11- to 14-fold by MK-801 treatment (p < 0.01). The ventrolateral thalamus of MK-801-treated rats showed almost complete histologic protection, and neocortical damage was reduced by 71% (p < 0.01). The degree of MK-801 protection of striatal neurons was less complete than that seen in other vulnerable structures, amounting to 63% for central striatum (p = 0.02, Mann-Whitney U test) and 48% in the dorsolateral striatum (NS). A repeated-measures analysis of variance demonstrated a highly significant overall protective effect of MK-801 treatment (F1,10 = 37.2, p = 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Blood Glucose; Brain Diseases; Carotid Arteries; Cerebral Cortex; Constriction; Corpus Striatum; Dizocilpine Maleate; Hippocampus; Ischemic Attack, Transient; Male; Neurons; Rats; Rats, Wistar; Thalamus; Time Factors

The effects of MK-801 on postischemic recovery, survival and neuronal preservation in the cortex, hippocampus and striatum were studied in Mongolian gerbils. The drug was administered 30 min prior to 20 of min forebrain ischemia induced by bilateral ligation of the carotids. Neurological recovery and survival were monitored for 7 days. At the end of the monitoring period neuronal damage was analyzed in the brains of the survivors in both groups. Treatment with MK-801 did not improve either neurological recovery or end-point survival. However, significant (P < 0.01) neuronal protection was observed in the hippocampi and striata of the drug treated animals while cortical neurons were not significantly protected. These findings demonstrate that protection against ischemic neuronal damage can be observed without concomitant improvement in either postischemic neurological recovery or survival. Protection of selectively vulnerable brain regions, often used as the predictor of the therapeutic potential of an agent, does not appear to correlate well with postischemic survival in this animal model of ischemia.

Topics: Animals; Blood Pressure; Body Temperature; Cardiac Output; Cell Survival; Dizocilpine Maleate; Female; Formaldehyde; Gerbillinae; Ischemic Attack, Transient; Neurons

The purpose of this study was to examine the protective effects of an N-methyl-D-aspartate receptor antagonist, MK-801, and pentobarbital against neuronal damage in a global ischemia model under controlled body temperature. Gerbils were subjected to 3 and 5 min of bilateral common carotid artery occlusion. MK-801 (1 and 5 mg/kg, i.p.), administered 30 min before ischemia, significantly attenuated the degeneration of hippocampal CA1 pyramidal cells after 3 min of ischemia in a dose dependent manner, but had no such effects after 5 min of ischemia. Pentobarbital (40 mg/kg, i.p.) also protected against CA1 damage after 3 min of ischemia but not after 5 min of ischemia. Thus, we confirmed the protective effects of these agents under normothermic conditions, although these effects were limited to shorter periods of ischemia.

Topics: Adenosine Triphosphate; Animals; Body Temperature; Carotid Artery, Common; Cell Death; Dizocilpine Maleate; Gerbillinae; Hippocampus; Ischemic Attack, Transient; Male; Neurons; Pentobarbital

The present study examined the functional changes in the hippocampal CA1 pyramidal cell system in vivo occurring after 12-min forebrain ischemia in the rat. A population excitatory postsynaptic potential and orthodromic population spike of CA1 pyramidal cells to stimulation of the Schaffer collaterals were potentiated at 6-8 h post-ischemia. These changes were not associated with an increase in excitability of the CA1 pyramidal cells as evaluated from the antidromic population spike induced by alveus stimulation, suggesting the presence of an increased synaptic efficacy. The post-ischemic potentiation was prevented by pretreatment with the N-methyl D-aspartate (NMDA) receptor antagonist, MK801, in a dose-dependent manner. These findings suggest that 12-min forebrain ischemia in the rat activates NMDA receptors, which results in an increase in synaptic efficacy to the CA1 pyramidal cells at 6-8 h post-ischemia.

Topics: Animals; Dizocilpine Maleate; Evoked Potentials; Hippocampus; Ischemic Attack, Transient; Male; Neuronal Plasticity; Prosencephalon; Rats; Rats, Wistar; Receptors, N-Methyl-D-Aspartate; Synapses

We examined the effect of blockade of N-methyl-D-aspartate (NMDA) and non-NMDA subtype glutamate receptors on anoxic depolarization (AD) and cortical spreading depression (CSD). [K+]e and the direct current (DC) potential were measured with microelectrodes in the cerebral cortex of barbiturate-anesthetized rats. NMDA blockade was achieved by injection of (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine maleate [MK-801; 3 and 10 mg/kg] or amino-7-phosphonoheptanoate (APH; 4.5 and 10 mg/kg). Non-NMDA receptor blockade was achieved by injection of 2,3-dihydroxy-6-nitro-7-sulfamoylbenzo(F)quinoxaline (NBQX; 10 and 20 mg/kg). MK-801 and APH blocked CSD, while NBQX did not. In control rats, the latency from circulatory arrest to AD was 2.1 +/- 0.1 min, while the amplitude of the DC shift was 21 +/- 1 mV, and [K+]e increased to 50 +/- 6 mM. All variables remained unchanged in animals treated with MK-801, APH, or NBQX. Finally, MK-801 (14 mg/kg) and NBQX (40 mg/kg) were given in combination to examine the effect of total glutamate receptor blockade on AD. This combination slightly accelerated the onset of AD, probably owing to circulatory failure. In conclusion, AD was unaffected by glutamate receptor blockade. In contrast, NMDA receptors play a crucial role for CSD.

Topics: 2-Amino-5-phosphonovalerate; Amino Acids; Animals; Cerebral Cortex; Cortical Spreading Depression; Dizocilpine Maleate; Electrophysiology; Ischemic Attack, Transient; Male; Quinoxalines; Rats; Rats, Inbred Strains; Receptors, Glutamate; Receptors, N-Methyl-D-Aspartate; Receptors, Neurotransmitter

After 6-12 h of recovery from transient cerebral ischemia, the pyramidal cells of the hippocampal CA1 region take up excessive amounts of calcium upon electrical stimulation, which has been suggested to be important for the development of delayed neuronal death. The aim of this study was to further characterize this enhanced calcium uptake with respect to time-course of development, relationship to neuronal damage, and amplitude of evoked field potentials as well as the dependency on N-methyl-D-aspartate (NMDA) and non-NMDA receptors. Adult Wistar rats were used and calcium-sensitive microelectrodes were placed in the stratum radiatum of the CA1 hippocampus for recording of the extracellular calcium concentration ([Ca2+]ec) during 20 min of ischemia and for 6 h of reflow. High-frequency stimulation of the perforant pathway elicited burst firing in CA1 and a transient decrease in [Ca2+]ec which reflects neuronal uptake. Shifts in [Ca2+]ec could not be evoked 0-1 h after ischemia. However, from 1-2 h burst firing could be evoked and the accompanying shift in [Ca2+]ec increased thereafter in amplitude with prolonged reflow, exceeded preischemic levels after 4 h, and reached 250 +/- 116% (mean +/- SD) of control after 6 h of reflow (p less than 0.05). The extracellular reference potential shift during electrical stimulation and the amplitude of evoked field potentials were still subnormal after 6 h [85 +/- 25% and 83 +/- 25%, respectively (mean +/- SD)]. There was a significant correlation between the degree of stimulated calcium uptake at 6 h postischemia and the extent of CA1 damage evaluated 7 days after the ischemic insult (r = 0.849; p less than 0.001). The shifts in [Ca2+]ec were reduced by the NMDA antagonist MK-801 (0.5-2 mg/kg, i.v.) to approximately 50% of the initial level during both control and postischemic conditions (p less than 0.01). The non-NMDA antagonist 2,3-dihydroxy-6-nitro-7-sulfamoylbenzo[F]quinoxaline (NBQX) (42 +/- 13 mg/kg, i.p.; mean +/- SD) decreased the amplitude of the evoked field potentials (to 30 +/- 28% of control, p less than 0.05) and completely abolished the evoked shifts in [Ca2+]ec. In conclusion, the uptake of calcium into CA1 pyramidal cells during electrical stimulation was enhanced already 4 h after ischemia in spite of the fact that other measures of excitability were subnormal. This calcium uptake correlated to the extent of CA1 pyramidal cell damage and was dependent on both NMDA and non-NMDA receptor activation.

Topics: Analysis of Variance; Animals; Calcium; Dendrites; Dizocilpine Maleate; Evoked Potentials; Hippocampus; Ischemic Attack, Transient; Male; Rats; Rats, Inbred Strains; Receptors, Amino Acid; Receptors, Cell Surface; Receptors, N-Methyl-D-Aspartate; Time Factors

1. Receptor autoradiographic and histological techniques were used to investigate long-term changes in the gerbil brain following transient cerebral ischaemia. 2. Transient ischaemia was induced for 3 min and 10 min, and the animals were allowed to survive for 8 months. 3. Histological examination revealed that 3 min ischaemia caused neuronal damage and mild shrinkage only in the hippocampal CA1 sector. Ten minutes of ischaemia produced severe neuronal damage in the striatum and the hippocampal CA1 and CA3 sectors. Considerable shrinkage was seen in the hippocampus; the dentate gyrus, however, was not damaged. 4. Three minutes of ischaemia produced changes in the binding of [3H]-quinuclidinylbenzilate ([3H]-QNB), [3H]-muscimol, and [3H]-MK-801 in various brain regions, as determined autoradiographically. In contrast, [3H]-cyclohexladenosine ([3H]-CHA) and [3H]-PN200-110 ([3H]-isradipine) binding in the brain was unaltered. 5. Ten minutes of ischaemia resulted in a major loss of neurotransmitter receptors, especially in the hippocampus. The substantia nigra showed a significant reduction in [3H]-CHA binding, whereas the striatum, which was morphologically damaged, showed no significant changes in any of the neurotransmitter receptors examined. 6. The results demonstrated that long-term survival after transient cerebral ischaemia produced alterations in neurotransmitter receptors, especially in the hippocampal formation, where considerable shrinkage was noted. These results also suggest that the hippocampal damage was not static, but progressive.

Topics: Adenosine; Animals; Autoradiography; Binding Sites; Brain; Dizocilpine Maleate; Gerbillinae; Hippocampus; Ischemic Attack, Transient; Isradipine; Male; Muscimol; Neurons; Quinuclidinyl Benzilate; Receptors, Neurotransmitter

Glutamatergic transmission is an important factor in the development of neuronal death following transient cerebral ischemia. In this investigation the effects of N-methyl-D-aspartate (NMDA) and non-NMDA receptor antagonists on neuronal damage were studied in rats exposed to 10 min of transient cerebral ischemia induced by bilateral common carotid occlusion combined with hypotension. The animals were treated with a blocker of the ionotropic quisqualate or alpha-amino-3-hydroxy-5-methyl-4-isoxazole (AMPA) receptor, 2.3-dihydroxy-6-nitro-7-sulfamoyl-benzo(F)quinoxaline (NBQX), given postischemia as an intraperitoneal bolus dose of 30 mg kg-1 followed by an intravenous infusion of 75 micrograms min-1 for 6 h, or with the noncompetitive NMDA receptor blocker dizocilpine (MK-801) given 1 mg kg-1 i.p. at recirculation and 3 h postischemia, or with the competitive NMDA receptor antagonist DL-(E)-2-amino-4-methyl-5-phosphono-3-pentenoic acid (CGP 40116), 5 mg kg-1, given intraperitoneally at recirculation. Treatment with NBQX provided a significant reduction of neuronal damage in the hippocampal CA1 area by 44-69%, with the largest relative decrease in the temporal part of the hippocampus. In neocortex a significant decrease in the number of necrotic neurons was also noted. No protection could be seen following postischemic treatment with dizocilpine or CGP 40116. Our data demonstrate that AMPA but not NMDA receptor antagonists decrease neuronal damage following transient severe cerebral ischemia in the rat and that the protection by NBQX may be dependent on the severity of the ischemic insult. We propose that the AMPA receptor-mediated neurotoxicity could be due to ischemia-induced changes in the control mechanisms of AMPA receptor-coupled processes or to changes of AMPA receptor characteristics.

Topics: 2-Amino-5-phosphonovalerate; Animals; Blood Glucose; Blood Pressure; Body Temperature; Cell Death; Dizocilpine Maleate; Hippocampus; Ischemic Attack, Transient; Male; Neurons; Quinoxalines; Rats; Receptors, AMPA; Receptors, N-Methyl-D-Aspartate; Receptors, Neurotransmitter

Increased extracellular concentrations of glutamate during episodes of cerebral ischemia may be due in part to a positive glutaminergic feedback loop. We evaluated the effect of selective AMPA or NMDA receptor antagonists on hippocampal extracellular concentrations of excitatory amino acids during ischemia and reperfusion. Thirteen New Zealand white rabbits were subjected to 10 min of global cerebral ischemia produced by neck tourniquet inflation (20 psi) combined with systemic hypotension during halothane (1-1.5%) anesthesia. Hippocampal extracellular concentrations of glutamate, aspartate, and glycine were monitored using in vivo microdialysis. NBQX (a selective AMPA receptor antagonist), MK801 (a noncompetitive NMDA receptor antagonist), or 5% dextrose was administered starting 1 h before ischemia. The NBQX group (n = 4) received 5 mg.kg-1 of NBQX intravenously (dissolved in 5% dextrose) over 5 min followed by an infusion of 5 mg.kg-1.h-1. The 5% dextrose group (n = 4) received an equivalent volume of 5% dextrose. The peak concentrations of glutamate, aspartate, and glycine in the early reperfusion period were 5-8-fold, 9-10-fold, and 4-5-fold higher than preischemic values, respectively. There were no significant differences, however, among the three groups in the concentrations of glutamate, aspartate, or glycine at any time during the study. These results do not support the existence of a positive feedback loop for glutamate mediated via AMPA or NMDA autoreceptors in the hippocampus during transient global ischemia or reperfusion.

Topics: Animals; Aspartic Acid; Dizocilpine Maleate; Glutamates; Glutamic Acid; Glycine; Hippocampus; Ischemic Attack, Transient; Quinoxalines; Rabbits; Receptors, AMPA; Receptors, N-Methyl-D-Aspartate; Receptors, Neurotransmitter; Reperfusion

Focal brain ischemia was induced by middle cerebral artery occlusion in the rat. The volume of cerebral damage was determined 2 days later by MRI in vivo and in the same animals histologically. The edema volume as measured by MRI and the histologically determined infarction was highly correlated. As a consequence, the neuroprotective effect of the N-methyl-D-aspartate (NMDA) receptor antagonists CGP 40116 and MK 801 were similar with both methods. Excitotoxic neurodegeneration in the rat striatum was induced by direct injection of quinolinic acid. The degree of damage was evaluated in vivo 1 day later by quantitative MRI, and 7 days later by measuring the activities of neuronal marker enzymes choline acetyltransferase and glutamic acid decarboxylase. Striatal damage assessed using the three approaches was highly correlated. Cerebroprotective efficacy of the NMDA receptor antagonist CGP 40116 was indistinguishable based on all methods. MRI was more reproducible than the enzymatic methods and was faster and simpler than histologic examination for routine analysis of excitotoxic damage and cerebroprotection in vivo in a pharmaceutical research environment.

Topics: 2-Amino-5-phosphonovalerate; Animals; Brain; Cerebral Arteries; Choline O-Acetyltransferase; Clinical Enzyme Tests; Constriction; Dizocilpine Maleate; Glutamate Decarboxylase; Ischemic Attack, Transient; Magnetic Resonance Imaging; Nerve Degeneration; Quinolinic Acid; Rats; Rats, Inbred F344

The non-competitive N-methyl-D-aspartate receptor/channel antagonist dizocilipine maleate (MK-801) has been reported to reduce infarct volume in a variety of focal stroke models. We examined the effect of MK-801 on infarct volume and cerebral blood flow in temporary and permanent focal ischemia in rats. In Wistar rats exposed to permanent right common carotid artery and 2 h of transient right middle cerebral and left common carotid artery occlusion followed by 22 h of reperfusion, MK-801 reduced infarct volume by 73% (P less than 0.05) and significantly increased cerebral blood flow to the ischemic core throughout the 2-h period of ischemia. In spontaneously hypertensive rats (SHRs) exposed to permanent right common carotid artery occlusion and 2 h of transient right middle cerebral artery occlusion followed by 22 h of reperfusion, MK-801 decreased infarct volume by 13% (P greater than 0.05) and increased cerebral blood flow to the penumbral region. In SHRs subjected to permanent right common carotid and middle cerebral artery occlusion MK-801 reduced infarct volume by 18% at 3 h (P greater than 0.05), by 25% at 6 h (P less than 0.01) and by 18% at 24 h (P less than 0.05). MK-801-treated SHRs had no difference in cerebral blood flow to the ischemic core, but increased cerebral blood flow to penumbral zones as compared with untreated SHRs. These results suggest that the protective effect of MK-801, at least in part, relates to improved cerebral blood flow.

Topics: Animals; Cerebral Infarction; Cerebrovascular Circulation; Cerebrovascular Disorders; Dizocilpine Maleate; Ischemic Attack, Transient; Male; Rats; Rats, Inbred Strains; Receptors, N-Methyl-D-Aspartate

A 5-min period of cerebral ischemia increased the number of errors (attempts to pass through two incorrect panels of the three panel-gates at four choice points) assessed by the working memory procedure applied in a three-panel runway task. The selective and competitive N-methyl-D-aspartate (NMDA) receptor antagonist CGS 19755 (3.2 and 10 mg/kg), administered i.p. immediately after blood flow reperfusion, significantly reduced the increase in errors expected to occur 24 h after 5 min of ischemia. CGS 19755 10 mg/kg had no effect on the increase in errors when injected 6 h after ischemia. The i.p. administration of the non-competitive NMDA antagonists dextrorphan 10 and 32 mg/kg and MK-801 1.0 mg/kg immediately after reperfusion decreased the increase of errors in the ischemic rats. The protective effects of NMDA antagonists suggest that the mechanism mediated by NMDA receptors during the early reperfusion phase plays a pivotal role in the postischemic impairment of working memory.

Topics: Animals; Dextrorphan; Dizocilpine Maleate; Ischemic Attack, Transient; Memory; N-Methylaspartate; Pipecolic Acids; Prosencephalon; Rats; Receptors, N-Methyl-D-Aspartate

The effects of dizocilipine maleate (MK-801), a noncompetitive N-methyl-D-aspartate (NMDA) receptor/channel antagonist, were tested on the dysfunction of neurotransmitter and signal transduction systems and morphological damage 7 days after transient forebrain ischemia in gerbils. Neurotransmitter system (adenosine A1, muscarinic cholinergic receptor) and signal transduction system (inositol 1,4,5-trisphosphate receptor: IP3, protein kinase C: PKC, L-type calcium channels) binding sites were mapped by in vitro quantitative receptor autoradiography. All ligands used in the present study decreased significantly in the CA1 subfield 7 days after ischemia. In normothermic animals, pretreatment with MK-801 failed to protect against decreased receptor binding in the hippocampus 7 days after ischemia. Moreover, in a morphological study, pre- and posttreatment of MK-801 failed to show protective effects against ischemic neuronal damage. On the other hand, pretreatment of MK-801, without maintaining body temperature, prevented the neuronal death of CA1 subfield 7 days after ischemia. These results weaken the hypothesis that NMDA receptor/channel may play a pivotal role in the pathogenesis of neuronal damage after transient forebrain ischemia.

Topics: Animals; Autoradiography; Body Temperature; Dizocilpine Maleate; Gerbillinae; Hippocampus; Hyperthermia, Induced; Ischemic Attack, Transient; Male; Neurons; Pyramidal Tracts; Reperfusion; Signal Transduction

The purpose of the present study was to examine the dose-response relationship and the maximum time for which effective therapy could be delayed for the N-methyl-D-aspartate antagonist dizocilpine (MK-801) as a neuroprotective agent in a permanent focal ischaemia model in the rat. The ED50 for dizocilpine in the amelioration of cortical damage in this model was found to be approximately 0.3 mg/kg (single i.p. dose, 30 min post onset of ischaemia) and significant protection was only obtained when therapy (3 mg/kg i.p.) was delayed for one hour or less after the onset of ischaemia. In a further experiment, dizocilpine 3 mg/kg i.p., produced a peak plasma level of 44 ng/ml and had a t1/2 elimination of 1.65 h.

Topics: Analysis of Variance; Animals; Brain; Dizocilpine Maleate; Dose-Response Relationship, Drug; Injections, Intraperitoneal; Ischemic Attack, Transient; Male; Rats; Rats, Inbred Strains

The clinical utility of N-methyl-D-aspartate (NMDA) receptor antagonists is now being assessed in ischemic brain injury in humans. The uptake and retention of NMDA receptor antagonists in ischemic tissue will influence the design of clinical trials. The effects of permanent occlusion of the middle cerebral artery, induced 15 minutes prior to isotope administration, on the uptake of 3H-MK-801 (dizocilpine) have been assessed in the rat with quantitative autoradiography. In a group of three rats at 15 minutes after the intravenous administration of 3H-MK-801, the level (mean +/- standard error of the mean) of isotopic tracer in the ischemic cortex and striatum was markedly less than that in the contralateral hemisphere (ipsilateral vs. contralateral caudate nucleus: 22 +/- 4 vs. 84 +/- 11 pmol/gm, p less than 0.01). In contrast, in a group of five rats at 60 minutes after the intravenous administration of 3H-MK-801, the level of isotopic tracer in the ischemic cortex and striatum was greater than that in the contralateral hemisphere (ipsilateral vs. contralateral caudate nucleus: 52 +/- 8 vs. 32 +/- 4 pmol/gm, p less than 0.05). There were no significant alterations in the specific binding of 3H-MK-801 in vitro in ischemic tissue at equivalent times. The early uptake of 3H-MK-801 into the central nervous system is dominated by the level of cerebral blood flow, whereas at later times after administration enhancement of MK-801 binding by elevated extracellular glutamate concentrations appears to be more important in determining the level of the drug in ischemic tissue.

Topics: Animals; Autoradiography; Dizocilpine Maleate; In Vitro Techniques; Ischemic Attack, Transient; Male; Radioligand Assay; Rats; Rats, Inbred Strains; Receptors, N-Methyl-D-Aspartate; Tritium

Delayed neuronal death induced by transient forebrain ischemia in the rat hippocampus is preceded by a prominent microglial reaction which begins within minutes after the ischemic injury. In the present study we have examined the effect of the non-competitive N-methyl-D-aspartate (NMDA) receptor antagonist MK-801 on microglial activation and neuronal survival. Using lectin histochemistry to detect microglia, we show that the systemic administration of MK-801 prior to ischemia prevents microglial activation, as well as delayed death of CA1 pyramidal neurons. The results demonstrate that early blockage of the glutamate cascade prevents microglial activation, and could suggest a role for microglia in mediating ischemic injury.

Topics: Animals; Dizocilpine Maleate; Female; Hippocampus; Ischemic Attack, Transient; Mesoderm; Prosencephalon; Rats; Rats, Inbred Strains; Receptors, N-Methyl-D-Aspartate

We explored the effectiveness of dual blockade of calcium channels in preventing ischemic necrosis in a rat model of transient forebrain ischemia.. To assess all the major brain regions, the entire brain was subserially sectioned and examined histologically 1 week after ischemia in 44 male Wistar rats. Brain temperature was monitored and controlled to avoid hypothermia or intergroup temperature differences at the time drugs were administered. All regimens were begun 20 minutes after ischemia. Treated animals received either the L-type calcium channel blocker nimodipine (0.25 microgram/min x 24-hour i.v. infusion), the noncompetitive N-methyl-D-aspartate receptor antagonist MK-801 (dizocilpine; 5 mg/kg i.v.), or both regimens in combination.. In the neocortex (p less than 0.05) and striatum (p less than 0.05), only double-treated animals showed a statistically significant reduction in neuronal necrosis. Dual therapy eliminated neuronal necrosis in the caudate nucleus entirely. In the septal (densely ischemic) hippocampus, protection was weak and inconsistent (0.012 less than p less than 0.788), but in the temporal (incompletely ischemic) hippocampus, the dual-treated group showed the most significant reduction (p less than 0.006).. We conclude that the combination of nimodipine and MK-801, if begun 20 minutes after ischemia, may offer a neuroprotective effect against neuronal necrosis in transient forebrain ischemia and that protection is maximal in the major extrahippocampal brain regions.

Topics: Animals; Brain; Dizocilpine Maleate; Drug Combinations; Ischemic Attack, Transient; Male; Necrosis; Nimodipine; Rats; Rats, Inbred Strains

In situ hybridization was used to study expression of mRNAs for members of the nerve growth factor (NGF) family in the rat brain after 2 and 10 min of forebrain ischemia and 1 and 30 min of insulin-induced hypoglycemic coma. Two hours after the ischemic insults, the level of brain-derived neurotrophic factor (BDNF) mRNA was markedly increased in the granule cells of the dentate gyrus, and at 24 h it was still significantly elevated. NGF mRNA showed a pronounced increase 4 h after 2 min of ischemia but had returned to a control level at 24 h. Both 2 and 10 min of ischemia caused a clear reduction of the level of mRNA for neurotrophin 3 (NT-3) in the dentate granule cells and in regions CA2 and medial CA1 of the hippocampus 2 and 4 h after the insults. The increase of BDNF mRNA could be partially blocked by the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor antagonist NBQX but was not influenced by the N-methyl-D-aspartate (NMDA) receptor antagonist MK-801. Both NBQX and MK-801 attenuated the decrease of NT-3 mRNA after ischemia. One and 30 min of hypoglycemic coma also induced marked increases in BDNF and NGF mRNA in dentate granule cells with maximal levels at 2 h. If the changes of mRNA expression lead to alterations in the relative availability of neurotrophic factors, this could influence functional outcome and neuronal necrosis following ischemic and hypoglycemic insults.

Topics: Animals; Brain; Brain-Derived Neurotrophic Factor; Dizocilpine Maleate; Gene Expression; Hippocampus; Insulin Coma; Ischemic Attack, Transient; Male; Nerve Growth Factors; Nerve Tissue Proteins; Neurotrophin 3; Nucleic Acid Hybridization; Proto-Oncogene Proteins c-fos; Quinoxalines; Rats; Rats, Inbred Strains; RNA, Messenger; Time Factors

Recent studies have demonstrated that measurement of peripheral type benzodiazepine binding sites (PTBBS) levels may be useful as an index for quantification of neuronal damage. In the present study, we investigated the accuracy of this index as a marker of neuronal damage induced by transient forebrain ischemia in the rat (4-vessel occlusion model). Seven days after ischemia, a good correlation was found between the increase of PTBBS levels (measured using [3H]PK 11195 as a specific radioligand) in hippocampal, striatal and cortical homogenates and the duration of ischemia. The progression of PTBBS increase was examined from 3 h to 14 days of recirculation. Increase in the maximal number of binding sites (Bmax) rather than an effect on the affinity (KD) for the radioligand was found in the 3 brain regions. Treatment of the animals with 1,3 butanediol (BD) prior to ischemia resulted in a neuroprotective effect as assessed by an improved neurological score and histological studies. The protective effect of BD was also correlated with a reduced expression of PTBBS as compared to ischemic animals not treated with the drug. No protective effects, on neurological score or PTBBS level were afforded by MK-801, a noncompetitive N-methyl-D-aspartate (NMDA) antagonist, R-phenylisopropyladenosine (RPIA), an adenosine A1 receptor agonist, or BN 52021, an antagonist of platelet-activating factor (PAF). These results suggest that PTBBS provide a useful marker of neuronal damage in a transient forebrain ischemia model and confirm the beneficial effect on ischemic damage exerted by BD.

Topics: Animals; Butylene Glycols; Diterpenes; Dizocilpine Maleate; Ginkgolides; Ischemic Attack, Transient; Lactones; Male; Neurons; Peripheral Nerves; Phenylisopropyladenosine; Prosencephalon; Radioligand Assay; Rats; Rats, Wistar; Receptors, GABA-A; Time Factors

Topics: Animals; Arginine; Cell Death; Cerebral Infarction; Dizocilpine Maleate; Ischemic Attack, Transient; Mice; Neurons; Nitric Oxide; Nitroarginine; Signal Transduction

This study compared the ability of three N-methyl-D-aspartate (NMDA) receptor antagonists to prevent neuronal degeneration in an animal model of global cerebral ischemia. The model employed is characterized by damage to the striatum, hippocampus, and neocortex. Antagonists were administered to gerbils either before or after a 5-min bilateral carotid occlusion. The intraischemic rectal temperature was either maintained at 36-37 degrees C or allowed to fall passively to 28-32 degrees C. Antagonists and doses tested were 1 and 10 mg/kg of MK-801 (pre- or postischemia), 30 mg/kg of CGS 19755 preischemia, four 25 mg/kg doses of CGS 19755 administered between 0.5 and 6.5 h postischemia, and 40 mg/kg of MDL 27,266 (pre- or postischemia). All three NMDA receptor antagonists exhibited some degree of neuroprotective activity when the carotid occlusion was performed under normothermic conditions. Most of the treatments with antagonist markedly reduced striatal damage. CA1 hippocampal and neocortical pyramidal cells were spared by only three of the treatments, however, and the extent of neuroprotection varied widely from case to case. Toxic doses of antagonist were required to protect CA1 pyramidal cells from ischemic damage. Ischemic damage to hippocampal areas CA2-CA3a and CA4 appeared to be resistant to all of these treatments. Most CA1 pyramidal cells that were protected from degeneration by an NMDA receptor antagonist were histologically abnormal. The neuroprotective effects of MK-801 and intraischemic hypothermia appeared to be additive. MK-801 (10 mg/kg) consistently reduced the postischemic brain temperature, but only the magnitude of hypothermia produced soon after reperfusion correlated with its neuroprotective action. These results suggest that NMDA receptor antagonists are relatively poor neuroprotective agents against a moderately severe ischemic insult.

Topics: Animals; Body Temperature; Brain; Cerebral Cortex; Corpus Striatum; Dizocilpine Maleate; Gerbillinae; Hippocampus; Ischemic Attack, Transient; Male; Neurons; Pipecolic Acids; Receptors, N-Methyl-D-Aspartate; Triazoles

Excessive activation of glutamate receptors, most notably the N-methyl-D-aspartate (NMDA) subtype, appears to be a crucial factor in the sequence of cellular events which lead to irreversible ischaemic damage to neurones. The ability of newly developed antagonists of the NMDA receptor to reduce ischaemic brain damage has been assessed in cat and rodent models of focal cerebral ischemia. Non-competitive NMDA receptor antagonists such as dizocilpine (CAS 77086-21-6) which act at a site within the receptor operated ion channel markedly reduce (by more than 50%) ischaemic brain damage when administered prior to the ischaemic episode or 2 h after the onset of ischaemia. Competitive NMDA receptor antagonists, such as D-(E)-4-(3-phosphonoprop-2-enyl)piperazine-2-carboxylic acid, which act at the neurotransmitter recognition site are equally effective in reducing the ischaemic brain damage when administered prior to the onset of the ischaemic episode. The clinical utility of competitive and non-competitive NMDA receptor antagonists in man will, however, be determined not by their tremendous anti-ischaemic efficacy, but by their profile of adverse effects. Careful selection of the therapeutic target for NMDA antagonists will be necessary if beneficial effects are to be established in man.

Topics: Animals; Cats; Cerebral Arteries; Dextrorphan; Dizocilpine Maleate; Hematoma, Subdural; Ischemic Attack, Transient; Kynurenic Acid; Phencyclidine; Piperazines; Rats; Receptors, N-Methyl-D-Aspartate

The purpose of this study was to determine whether prior transient cerebral ischemia, in conscious mice, would alter the biological responses resulting from excessive activation of N-methyl-D-aspartate (NMDA) receptors, in an early stage. The responses to the activation of NMDA receptors by an intracerebroventricular injection of NMDA, such as wild running, tonic and clonic convulsions, absence of the visual placing reflex, loss of the righting reflex, impaired motor function and a high mortality rate, were to a large extent prevented if 30 min before treatment, either a 10-min period of global cerebral ischemia was induced or a 1 nmol intraventricular injection of NMDA was given but not if either of the above procedures was done one day before the test dose of NMDA. In contrast, behavioral symptoms, in response to activation of non-NMDA-type glutamate receptors elicited by intraventricular injection of either kainic acid or AMPA, were not clearly affected. Transient systemic hypercapnic anoxia (22-sec exposure to 100% CO2 gas), before treatment with NMDA did not significantly reduce the NMDA-induced behavior. The severity of these behavioral responses and high mortality rate observed after intraventricular injection of pentylenetetrazole (PTZ, 30 mumol) were not altered by either prior global ischemic insult or by a preexposure to NMDA given intraventricularly. The NMDA antagonist, MK801 (0.1 and 0.3 mg/kg i.p.) greatly reduced the behavioral effects and mortality rate, resulting from the intraventricular injection of NMDA and somewhat reduced the effects of the intraventricular injection of PTZ.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Behavior, Animal; Carbon Dioxide; Dizocilpine Maleate; Female; Hypoxia; Injections, Intraventricular; Ischemic Attack, Transient; Mice; Mice, Inbred Strains; N-Methylaspartate; Nerve Degeneration; Pentylenetetrazole; Receptors, N-Methyl-D-Aspartate; Survival Rate

Glutamate is an important factor in the mechanisms of neuronal damage following cerebral ischemia. Blockade of one type of glutamate receptor, the N-methyl-D-aspartate (NMDA) receptor, decreases brain infarct size in experimental models of permanent focal ischemia, but protection in models of transient reversible ischemia is ambiguous. We investigated the effect of the noncompetitive NMDA receptor antagonist dizocipiline (MK-801) on neuronal damage in the CA1 region of the rat hippocampus, using two models of reversible cerebral ischemia: 10 or 15 min of bilateral common carotid occlusion combined with hypotension, or 6-8.5 min of cardiac arrest. Histopathologic evaluation of neuronal damage was performed 7 days after the ischemic insults. Thirteen groups of rats (a total of 129 animals) were treated with saline or dizocilpine in single or multiple doses ranging from 0.1 to 5 mg.kg-1, given intravenously or intraperitoneally prior to and/or after the ischemic insult. In none of the dizocilpine-treated groups could neuronal protection be demonstrated in the CA1 region of the septal as well as dorsotemporal hippocampus, compared to a corresponding saline-treated group. We conclude that systemically administered noncompetitive NMDA receptor antagonists do not provide a marked protection against neuronal damage after a transient period of severe forebrain ischemia.

Topics: Animals; Blood Glucose; Blood Pressure; Body Temperature; Cerebrovascular Circulation; Dizocilpine Maleate; Infusions, Intravenous; Injections, Intraperitoneal; Ischemic Attack, Transient; Male; Rats; Rats, Inbred Strains

c-Fos protein expression was examined in brain by immunohistochemistry following permanent middle cerebral artery (MCA) occlusion above the rhinal fissure and ipsilateral common carotid artery (CCA) occlusion in Long-Evans rats. In sham-operated animals, c-fos protein-like immunoreactivity (CFPLI) was confined to neuronal nuclei of the hypothalamus and was not present in other regions including cerebral cortex. In the core territory of the MCA, CFPLI was not detected when examined at 15 and 30 min, 1, 4 and 8 h and 1, 2, 4 and 7 days after occlusion. Focal ischemia induced two temporal and spatial patterns of CFPLI. At 1 h, c-fos protein was expressed in the nuclei of many neurons in layers II-V of the ipsilateral cortex both immediately adjacent to and remote from the ischemic territory. Within regions outside the MCA territory (e.g. cingulate gyrus and piriform cortices), CFPLI in these neurons peaked at 2-4 h and was undetectable after 2 days. Neurons in the zone immediately surrounding the ischemic core within MCA territory also expressed CFPLI, but in contrast, continued to express c-fos up to 4 days after ischemia. Immunoreactivity surrounding the ischemic core was found in neuronal nuclei predominantly, although from 1 to 4 days, CFPLI was found in perikarya and dendrites as well. MK-801 (3 mg/kg, i.p., 30 min prior to occlusion) completely blocked the early c-fos protein induction in all regions but expression within neurons surrounding the ischemic core was present 1 day after a single injection.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Carotid Arteries; Cerebral Cortex; Dizocilpine Maleate; Functional Laterality; Immunoenzyme Techniques; Immunohistochemistry; Ischemic Attack, Transient; Proto-Oncogene Proteins c-fos; Rats

The effects of the calcium channel blocker nimodipine and the non-competitive NMDA-antagonists MK-801 and phencyclidine (PCP) on infarct size 48 h after occlusion of the middle cerebral artery (MCA-O) were evaluated in the rat. Nimodipine was given at a dose of 0.3 mg/kg s.c. 30 min prior and 8, 16, and 24 h after MCA-O. MK-801 (1 mg/kg i.p. or 10 mg/kg i.p.) or PCP (0.3, 1.0, 3.0, 10, or 30 mg/kg i.p.) were administered 30 min prior to ischemia. In additional experiments 30 mg/kg PCP was given 1, 3, or 5 h post ischemia. Nimodipine and 1 mg/kg MK-801 reduced cortical infarct volumes significantly by 50% and 55%, respectively, while cortical infarct size fell by 32% and total infarct volume was not altered significantly after administration of 10 mg/kg MK-801. Pretreatment with 10 or 30 mg/kg PCP reduced cortical infarction by 47-53% and total infarct volumes by 39-42%. Posttreatment with PCP was effective if started at 1 or 3 h post ischemia.

Topics: Animals; Blood Glucose; Blood Pressure; Carbon Dioxide; Cerebral Arteries; Cerebral Infarction; Dizocilpine Maleate; Ischemic Attack, Transient; Nimodipine; Oxygen; Partial Pressure; Phencyclidine; Rats; Rats, Inbred F344; Time Factors

The neuroprotective effects of dizocilipine maleate (MK-801), a noncompetitive antagonist of the N-methyl-D-aspartate (NMDA) receptor/channel, were tested in the 4-vessel occlusion rat model of forebrain ischemia. Adult Wistar rats, treated intraperitoneally with MK-801 or saline using several different treatment paradigms were subjected to 5 (n = 208) or 15 (n = 62) min of severe, transient forebrain ischemia. In saline-treated animals, 15 min of ischemia (n = 13) produced extensive and consistent loss of pyramidal neurons in the CA1 zone of hippocampus. The degree and distribution of cell loss were not reduced by single dose preischemic administration of MK-801 at 1 (n = 7), 2.5 (n = 4), or 5 mg/kg (n = 8). In other animals subjected to 15 min of forebrain ischemia, multiple doses of MK-801 (5, 2.5, and 2.5 mg/kg) given immediately and at approximately 8 and 20 hr after cerebral reperfusion (n = 5) did not alter CA1 injury compared to saline-treated controls (n = 5). Five minutes of forebrain ischemia in saline-treated animals, (n = 82) resulted in significantly fewer (p less than 0.001) dead CA1 pyramidal cells and a greater variance compared to animals subjected to 15 min of ischemia. Power analysis of the preliminary saline-treated animals subjected to 5 min of ischemia (n = 22) indicated that 60 animals per group were necessary to detect a 15% difference between MK-801 and vehicle-treated groups. Multidose treatment with MK-801 (1 mg/kg) given 1 hr prior to 5 min of ischemia (n = 60) and again at approximately 8 and 16 hr after recirculation failed to attenuate hippocampal injury.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Behavior, Animal; Cell Survival; Dizocilpine Maleate; Dose-Response Relationship, Drug; Hippocampus; Ischemic Attack, Transient; N-Methylaspartate; Neurons; Rats; Sodium Chloride

Induction of mRNA encoding the 70 kDa stress/heat shock protein, hsp70, was evaluated in post-ischemic gerbil brain by in situ hybridization using an oligonucleotide probe selective for stress-inducible members of this gene family. Expression of hsp70 sequences was most pronounced in hippocampal CA1 neurons that fail to accumulate immunoreactive hsp70 protein, and that are selectively lost following ischemia. Hybridizable RNA continued to be expressed in CA1 through at least 48 h, essentially until the onset of cell death in this model. In contrast, dentate granule cells and CA2 neurons destined to survive the insult showed transient induction of hsp70 mRNA during the first 24 h of recirculation that disappeared prior to the detection of maximal hsp70 immunoreactivity in these cell populations. Pretreatment with a single injection of MK-801 (10 mg/kg) considerably attenuated the induction of hsp70 mRNA in hippocampus at 6 h of recirculation, an effect apparently mediated by persistent drug-induced hypothermia. The drug did not prevent the later, selective appearance of hsp70 hybridization in CA1 neurons at 24 h, nor did it protect against the subsequent loss of these cells. These results demonstrate a prolonged postischemic stress response at the transcriptional level in vulnerable hippocampal neurons, and suggest its utility as a marker for neuronal pathophysiology associated with mechanisms mediating delayed neuronal death.

Topics: Animals; Base Sequence; Body Temperature; Brain; Dizocilpine Maleate; Female; Gerbillinae; Heat-Shock Proteins; Hippocampus; Ischemic Attack, Transient; Kinetics; Molecular Sequence Data; Molecular Weight; Neurons; Nucleic Acid Hybridization; Oligonucleotide Probes; RNA, Messenger

Topics: Adenosine Triphosphate; Animals; Calmodulin; Dizocilpine Maleate; Energy Metabolism; Hippocampus; Imidazoles; In Vitro Techniques; Ischemic Attack, Transient; Ketamine; Kinetics; Rats

Release of glutamate from brain cells is increased during ischemia and is thought to be involved in ischemic damage. In rat hippocampal slices the release of glutamate during 'in vitro ischemia' (anoxia without glucose) is shown to be blocked by two groups of compounds: non-competitive N-methyl-D-aspartate (NMDA) antagonists and sigma ligands. The effects are selective for the ischemic glutamate release, which is independent of extracellular Ca2+. High K+, Ca2+ dependent, induced release of glutamate is not inhibited. NMDA receptor blockade normally does not prevent ischemic transmission damage in the rat hippocampal slice. However, when ischemic glutamate release is attenuated, NMDA receptor antagonists do prevent the damage. This indicates that high levels of glutamate may cause damage via non-NMDA as well as NMDA receptors.

Topics: 2-Amino-5-phosphonovalerate; Amino Acids; Animals; Anticonvulsants; Cyclazocine; Dizocilpine Maleate; Glutamates; Guanidines; Haloperidol; Hippocampus; In Vitro Techniques; Ischemic Attack, Transient; Ketamine; Kynurenic Acid; Male; Models, Neurological; Phencyclidine; Pyramidal Tracts; Rats; Rats, Inbred Strains; Receptors, N-Methyl-D-Aspartate; Receptors, Opioid; Receptors, sigma

Degeneration of hippocampal CA1 neurons occurs following transient complete ischemia produced by raised intracranial pressure. Both systemic injection of MK-801 and profound cerebral hypothermia produced by cisternal infusion of room temperature (22-25 degrees C) fluids protect vulnerable CA1 neurons from degeneration. Hypothermia appears to decrease hippocampal extracellular levels of glutamate during and after ischemia but provides only relative protection from ischemia as CA1 degeneration does occur with prolonged (30 min) periods of ischemia. Elevated intracranial pressure appears to produce ischemic degeneration in the hippocampus via an NMDA receptor mediated excitotoxic process which is highly temperature dependent.

Topics: Animals; Body Temperature Regulation; Dibenzocycloheptenes; Dizocilpine Maleate; Glutamates; Glutamic Acid; Hippocampus; Intracranial Pressure; Ischemic Attack, Transient; Male; Rats; Receptors, N-Methyl-D-Aspartate; Receptors, Neurotransmitter

The effect of treatment with the potent, non-competitive NMDA receptor-channel antagonist (+)-5-methyl-10,11-dihydro-5H-dibenzo[a, d] cyclohepten-5,10-imine maleate (MK-801) on ischemia-induced brain damage was studied in a well-characterized model of focal neocortical infarction in spontaneously hypertensive rats. Anesthesia exposure was minimized to the surgical procedure and the infarcts were allowed to mature over a 24-h period. Pretreatment with 5 mg/kg i.p. MK-801 (n = 11 control, n = 12 treated animals) 30 min before induction of focal cerebral ischemia had no statistically significant influence on infarct volumes. However, pre- and post-treatment with MK-801 5 mg/kg i.p. 30 min before induction of ischemia and 2.5 mg/kg each at 8 and 16 h after onset of ischemia, reduced infarct volumes in two separate studies by 29% (investigator J.T., n = 5 control and n = 7 treated animals) and 20% (investigator U.D., n = 8 control and n = 8 treated animals), respectively. The combined reduction in infarct volume in MK-801-treated animals for both investigators was 23% (P = 0.016, ANOVA). The findings indicate a smaller neuroprotective effect of MK-801 in spontaneously hypertensive rats subjected to focal ischemia than in previous reports using normotensive animals.

Topics: Animals; Behavior, Animal; Brain Damage, Chronic; Cerebral Cortex; Cerebral Infarction; Dizocilpine Maleate; Drug Administration Schedule; Hypertension; Ischemic Attack, Transient; Male; Monitoring, Physiologic; Rats; Rats, Inbred SHR; Receptors, N-Methyl-D-Aspartate

Topics: Animals; Anticonvulsants; Body Temperature; Brain; Brain Diseases; Carotid Arteries; Corpus Striatum; Disease Models, Animal; Dizocilpine Maleate; Gerbillinae; Hippocampus; Hypothermia; Ischemic Attack, Transient; Male; Pipecolic Acids; Pyramidal Tracts; Receptors, N-Methyl-D-Aspartate; Triazoles

The present study was designed to determine if the noncompetitive excitatory amino acid antagonist, dizocilpine maleate, when administered after a 17 min period of complete cerebral ischemia in primates, would improve postischemic neurologic function and hippocampal histopathologic outcome when compared to placebo-treated animals. Ten pigtail monkeys were anesthetized and subjected to complete cerebral ischemia using an established neck tourniquet model. Five minutes postischemia, five monkeys received dizocilpine 300 micrograms/kg i.v. over 5 min, followed by an infusion of 150 micrograms/kg/h for 10 h. This produced plasma levels of the drug in excess of 30 ng/ml for the duration of the infusion. An additional five monkeys were treated with an identical volume of saline placebo. All monkeys received intensive care for the initial 24 to 48 h postischemia. At 96 h postischemia, there was no significant difference in neurologic function between the two groups (p = 0.53, with the placebo group having the numerically better outcome). There also was no significant difference between hippocampal histopathology scores between dizocilpine and placebo-treated monkeys. The authors conclude that dizocilpine is not an efficacious therapy in the treatment of neurologic injury that occurs following complete cerebral ischemia in this primate model.

Topics: Animals; Brain; Dibenzocycloheptenes; Dizocilpine Maleate; Electroencephalography; Hippocampus; Ischemic Attack, Transient; Macaca nemestrina; Male; Pilot Projects; Receptors, N-Methyl-D-Aspartate; Receptors, Neurotransmitter

The non-competitive N-methyl-D-aspartate (NMDA) antagonist, MK-801, has been reported to prevent or attenuate ischemic brain damage in various animal models. In halothane-anesthetized gerbils it was found that an optimal dose of MK-801 (3.0 mg/kg) for providing cerebral protection also produced hypothermia (31.1 +/- 0.62 degrees C) relative to control animals (34.2 +/- 0.77 degrees C, P less than 0.01). This degree of hypothermia alone was sufficient to provide complete histological and functional protection (spatial memory) against 5 min of carotid artery occlusion. In gerbils made ischemic, but maintained at normal body temperature, a dose of 3.0 mg/kg of MK-801 provided no protection against hippocampal cell loss or spatial memory impairment. These data suggest that the protective actions of MK-801 may be due entirely to drug-induced hypothermia.

Topics: Animals; Body Temperature Regulation; Dibenzocycloheptenes; Dizocilpine Maleate; Female; Gerbillinae; Hypothermia; Ischemic Attack, Transient; Receptors, N-Methyl-D-Aspartate; Receptors, Neurotransmitter

Pretreatment with MK-801 (an NMDA antagonist) or pentobarbital (a GABAA receptor-effector) ameliorated histopathological neuronal damage to the hippocampal CA1 subfield and to the thalamus following three 2-min forebrain ischemia at 1-h intervals in the gerbil. Flunarizine, a calcium antagonist, failed to prevent the neuronal damage. The results suggest that the excitotoxic mechanism plays a role in the neuronal damage following repeated ischemia.

Topics: Animals; Dibenzocycloheptenes; Dizocilpine Maleate; Flunarizine; Gerbillinae; Ischemic Attack, Transient; Male; Pentobarbital; Receptors, GABA-A; Receptors, N-Methyl-D-Aspartate; Receptors, Neurotransmitter

The broad spectrum excitatory amino acid antagonist, kynurenic acid was evaluated in a transient forebrain ischaemia model in gerbils. When administered i.p., 15 min prior to a 5 min period of ischaemia, a dose-related neuroprotective effect was seen with 800 mg/kg of kynurenic acid showing very good protection. A combination of kynurenic acid (200 or 400 mg/kg) and MK-801 (0.1 mg/kg) gave a synergistic neuroprotective effect. Neither kynurenic acid (200 or 400 mg/kg) nor MK-801 (0.3 mg/kg) was neuroprotective when administered by itself 30 min post-ischaemically, but when co-administered significant protection of the CA1 pyramidal neurones of the hippocampus was seen. In addition, we examined the effect of maintaining core body temperature on the neuroprotective action of MK-801 and kynurenic acid following the suggestion that it was a hypothermic effect of MK-801 which resulted in neuroprotection in gerbils. When the body temperature of the gerbils was maintained at 37 degrees C for a period of 24 h it did not affect the neuroprotective action of MK-801 (0.1 or 10 mg/kg) or kynurenic acid (200 mg/kg).

Topics: Animals; Body Temperature; Brain; Carotid Arteries; Dibenzocycloheptenes; Dizocilpine Maleate; Drug Synergism; Gerbillinae; Ischemic Attack, Transient; Kynurenic Acid; Neurons; Pyramidal Tracts

The role of calcium as a mediator in neuronal death during ischemia is now quite strong. Evidence supporting this link includes studies in cell cultures and measurements of calcium accumulation in the mitochondria during ischemia, as well as direct measurements of shifts in extracellular calcium using microelectrodes. Since it is dangerously high concentrations of the intracellular free calcium that have been hypothesized to lead to neuronal damage, direct in vivo measurements of this parameter in ischemia are important. A technique for the measurement of intracellular free calcium is described, along with data from studies that dramatically demonstrate the time course of changes in intracellular free calcium induced by focal ischemia. Additional data are also presented that indicate that cellular damage can be attenuated by the use of agents that block calcium channels (nimodipine, which blocks voltage-sensitive calcium channels, and MK-801, which blocks receptor-operated channels) and support the concept that these agents owe their beneficial effects to their ability to reduce the accumulation of intracellular calcium.

Topics: Animals; Calcium; Cats; Cerebral Arteries; Cerebrovascular Circulation; Cerebrovascular Disorders; Cytosol; Dizocilpine Maleate; Electroencephalography; Ischemic Attack, Transient; Nimodipine

Several laboratories have reported a significant reduction of ischemia-induced injury to hippocampal neurons in rodents treated with competitive and noncompetitive N-methyl-D-aspartate (NMDA) receptor-channel antagonists. This study examined the effects of the noncompetitive antagonist (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine maleate (MK-801) in Mongolian gerbils subjected to 5 min of bilateral carotid artery occlusion. In adult female gerbils, single doses of MK-801 injected 1 hr prior to ischemia significantly (p less than 0.01) reduced damage to CA1 hippocampal neurons. However, the drug rendered the postischemic animals comatose and hypothermic for several hours compared with the saline-treated animals. In subsequent experiments, animals pretreated with MK-801 and maintained normothermic during and after forebrain ischemia demonstrated no amelioration of hippocampal damage. Gerbils not treated with MK-801, but kept hypothermic in the postischemic period to approximately the same degree (34.5 degrees C) and duration (8 hr) as was induced by MK-801 therapy showed significant (p less than 0.01) protection of CA1 neurons against ischemia. The neuroprotective activity of MK-801 against transient global ischemia appears to be largely a consequence of postischemic hypothermia rather than a direct action on NMDA receptor-channels.

Topics: Animals; Aspartic Acid; Body Temperature; Dibenzocycloheptenes; Dizocilpine Maleate; Female; Gerbillinae; Hypothermia, Induced; Ischemic Attack, Transient; N-Methylaspartate; Neurons

After 10-60 min of normothermic complete ischemia, hippocampal slices were prepared and allowed to recover for 60 min. The presence or absence of an evoked transsynaptic response was measured in CA1, CA3, and dentate gyrus. A selective vulnerability of the field excitatory postsynaptic potential to ischemia was found (CA1 greater than CA3 greater than dentate gyrus). Recovery of synaptic transmission in CA1 and CA3 was significantly improved by decreasing extracellular Ca2+ and increasing Mg2+ after ischemia. Addition of an N-methyl-D-aspartate antagonist further improved functional recovery. Postischemic reduction in extracellular Cl- increased recovery in CA1 and CA3, whilst reduction in Na+ was deleterious.

Topics: Animals; Calcium; Dibenzocycloheptenes; Dizocilpine Maleate; Guinea Pigs; Hippocampus; In Vitro Techniques; Ischemic Attack, Transient; Magnesium; Male; Receptors, N-Methyl-D-Aspartate; Receptors, Neurotransmitter; Synaptic Transmission

Accumulating evidence suggests that the N-methyl-D-aspartate (NMDA) subtype of glutamate receptor may play an important role in hypoxic/ischemic (H/I) brain damage. Accordingly, it has been shown that the NMDA antagonist, MK-801, partially protects the infant rat brain against H/I damage. Here we show that reducing the body temperature of the infant rat also confers partial protection against H/I brain damage and that mild hypothermia plus MK-801 treatment provides total protection against such damage. Relevance of these findings to the prevention of perinatal brain damage in humans is discussed.

Topics: Animals; Animals, Newborn; Anticonvulsants; Combined Modality Therapy; Dibenzocycloheptenes; Dizocilpine Maleate; Hypothermia, Induced; Ischemic Attack, Transient; Rats; Rats, Inbred Strains; Receptors, N-Methyl-D-Aspartate; Receptors, Neurotransmitter

Transient forebrain ischemia is followed within minutes by accelerated proteolysis of the cytoskeletal protein, spectrin. This effect is most pronounced in the selectively vulnerable CA1 region of hippocampus which also experiences a second proteolytic phase during the terminal stages of neuronal degeneration. Both proteolytic phases are suppressed by MK-801, an NMDA receptor antagonist. Cytoskeletal disruption, via NMDA receptor-linked proteolytic events, is suggested to predispose vulnerable neurons to delayed cell death.

Topics: Animals; Cytoskeletal Proteins; Dibenzocycloheptenes; Dizocilpine Maleate; Gerbillinae; Hippocampus; Ischemic Attack, Transient; Receptors, N-Methyl-D-Aspartate; Receptors, Neurotransmitter; Spectrin

The effect of the N-methyl-D-aspartate (NMDA) receptor antagonist dizociplipine maleate (MK-801) on cerebral blood flow (CBF), cerebral metabolic rate for oxygen (CMRO2), intracranial pressure and systemic variables was examined in 6 normal dogs (Group I). In 6 additional dogs (Group II), the effects of a prior 11 min episode of complete cerebral ischemia on the response to dizocilipine was studied. CBF was measured with a sagittal sinus outflow technique and CMRO2 was calculated as the product of CBF and the arterial to sagittal sinus O2 content difference. Dizocilipine was administered as a 150 micrograms/kg i.v. bolus followed by a 75 micrograms.kg-1.h-1 infusion for 90 min. Plasma dizocilipine levels were greater than 25 ng/ml for the duration of the infusion. The CSF levels were approximately half the plasma levels. Five minutes after initiation of dizocilipine treatment, Group I dogs experienced a 63% increase in heart rate (P less than 0.01) and an 8% decrease in the mean arterial blood pressure (P less than 0.05). Over the same time interval. CBF increased by 85% (P less than 0.01) and intracranial pressure nearly doubled (P less than 0.05). In addition, dizocilipine treatment in all Group I animals resulted in EEG quasiperiodic bursts of delta-waves and polyspikes on a background of beta-activity. With the exception of the intracranial pressure, the above changes in systemic and cerebral variables persisted for the duration of the drug infusion. Intracranial pressure was no longer significantly elevated after 80 min of drug infusion. Hemispheric CMRO2 was unchanged by dizocilipine in Group I dogs. There was a decrease in the cortical glucose level at the end of the study, but no significant change in phosphocreatine, ATP, lactate, or energy charge when compared with 6 laboratory normals. An identical dose of dizocilipine administered after an 11 min episode of complete cerebral ischemia resulted in no significant changes in either cerebral or systemic variables. The absence of systemic effects in Group II dogs suggests that dizocilipine administration in normal dogs results in a centrally mediated activation of the peripheral sympathetic nervous system. The uncoupling of CBF and CMRO2 observed following dizocilipine treatment is similar to that reported for two other known NMDA antagonists, ketamine and phencyclidine. If administration of dizocilipine results in improved histopathological and neurological outcome following an episode of complete

Topics: Animals; Brain; Cerebrovascular Circulation; Dibenzocycloheptenes; Dizocilpine Maleate; Dogs; Energy Metabolism; Female; Ischemic Attack, Transient; Male; Receptors, N-Methyl-D-Aspartate; Receptors, Neurotransmitter

Transient global ischemia was produced in rats by cisternal fluid infusion, producing a negative cerebral perfusion pressure by elevating the intracranial pressure (ICP) 25-50 mm Hg above mean arterial pressure (MAP). Animals were allowed to survive for 2-7 days following a transient ischemic episode of 5-30 min. The brains were examined for signs of ischemic degeneration in Nissl-stained sections and adjacent sections reacted with antisera against glial fibrillary acidic protein (GFAP) or aspartate aminotransferase (AAT). Neurons in the thalamic reticular nucleus (RT), a pure population of gamma-aminobutyric acid (GABA)ergic neurons which project their axons to thalamic relay nuclei, were found to have the lowest threshold for degeneration in this model, consistently undergoing degeneration under conditions which completely spared the hippocampal CA1 from degeneration. Whereas it took up to 30 min of complete ischemia to produce degeneration of CA1 neurons when ICP was raised using room temperature infusion fluids, 15 min of ischemia under these conditions was sufficient to produce extensive degeneration of neurons in the entire ventral 3/4 of the RT. Prolonged (greater than 25 min) episodes of partial ischemia (ICP less than or equal to MAP) were also sufficient to produce massive degeneration of RT neurons. The lesion in the RT was most clearly evident in sections reacted with antisera to GFAP, labeling intensely reactive protoplasmic astrocytes within the regions of the RT where neuronal degeneration had occurred. Neuronal loss and accompanying proliferation of microglial cells were evident in Nissl-stained sections but the extent of the neuronal loss was most clearly obvious in sections reacted with an antisera to AAT, an enzyme present in detectable quantities in GABAergic neurons. Pretreatment with the non-competitive NMDA antagonist MK-801 at doses sufficient to completely prevent massive degeneration of the hippocampal CA1 failed to prevent the degeneration of RT neurons, suggesting that if RT degeneration involves an excitotoxic process it acts through non-NMDA receptors.

Topics: Animals; Aspartate Aminotransferases; Dibenzocycloheptenes; Dizocilpine Maleate; gamma-Aminobutyric Acid; Intracranial Pressure; Ischemic Attack, Transient; Male; Rats; Receptors, N-Methyl-D-Aspartate; Receptors, Neurotransmitter; Thalamic Nuclei

The neuroprotective activity of two systemically administered N-methyl-D-aspartate (NMDA) receptor antagonists, ketamine and MK-801, were investigated in a long-term recovery model of near-complete forebrain ischemia in the rat. Doses of each drug were chosen on the basis of the known degree and time course of NMDA antagonism seen in vivo after their systemic administration. Ketamine, administered at a dose of 20 mg.kg-1 iv, either immediately before or shortly after the 10-min ischemic period, failed to lessen neuronal damage in the selectively vulnerable hippocampal CA1 region. Increasing doses of ketamine administered over an increasing length of time in the postischemic period, however, did provide significant protection. MK-801 0.25 or 0.5 mg.kg-1 iv administered before ischemia also resulted in significant protection. The results support the proposal that NMDA receptor-mediated events may contribute to neuronal damage in selectively vulnerable regions of the central nervous system after ischemia.

Topics: Animals; Dibenzocycloheptenes; Dizocilpine Maleate; Ischemic Attack, Transient; Ketamine; Neurons; Rats; Rats, Inbred Strains; Receptors, N-Methyl-D-Aspartate; Receptors, Neurotransmitter

Excessive activation of the N-methyl-D-aspartate (NMDA) subtype of glutamate receptor has been implicated in the sequence of neurochemical events that results in irreversible neuronal damage in cerebral ischemia. The effects of the NMDA antagonist (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine maleate (MK-801) upon the amount of ischemic brain damage has been assessed quantitatively in the lightly anesthetized rat. Focal cerebral ischemia was produced by the permanent occlusion of one middle cerebral artery (MCA), and the animals were killed 3 hours after the arterial occlusion. MK-801 (0.5 mg/kg) was administered intravenously either 30 minutes prior to MCA occlusion or 30 minutes after the induction of ischemia. Pretreatment with MK-801 reduced the volume of ischemic damage both in the cerebral cortex (by 38% compared with untreated rats with MCA occlusion; p less than 0.01) and in the caudate nucleus (by 18% compared with controls; p less than 0.05). Treatment with MK-801, initiated 30 minutes after MCA occlusion, reduced the volume of ischemic damage in the cerebral cortex (by 52% compared with controls; p less than 0.01). The volume of ischemic damage in the caudate nucleus was minimally influenced by MK-801 treatment initiated after MCA occlusion. The antiischemic effects of MK-801 were readily demonstrable despite the hypotension that MK-801 induced in rats anesthetized with halothane (0.5%), nitrous oxide (70%), and oxygen (30%). The potency of MK-801 in reducing ischemic brain damage, even when administered after the induction of ischemia, highlights the potential use of NMDA receptor antagonists for the treatment of focal cerebral ischemia in humans.

Topics: Animals; Blood Pressure; Dibenzocycloheptenes; Dizocilpine Maleate; Ischemic Attack, Transient; Male; Rats; Rats, Inbred Strains; Receptors, Glutamate; Receptors, Neurotransmitter

The effects of the glutamate N-methyl-D aspartate (NMDA) receptor antagonist, MK-801, upon ischemic brain damage has been examined in anesthetized cats. Focal cerebral ischemia was produced by permanent occlusion of one middle cerebral artery and the animal were killed 6 h later. The amount of early ischemic damage was assessed in coronal sections at 16 predetermined stereotactic planes. Pretreatment with MK-801 (5 mg/kg, i.v.), 30 min before occlusion of the middle cerebral artery significantly reduced the volume of ischemic damage (from 32.7 +/- 4.0% of the cerebral hemisphere in vehicle-treated cats to 16.2 +/- 4.5% in MK-801-treated cats). NMDA receptor antagonists that penetrate the blood-brain barrier, such as MK-801, merit further study as protective agents against ischemic brain damage.

Topics: Animals; Blood Pressure; Brain; Cats; Cell Nucleus; Cerebral Cortex; Cytoplasm; Dibenzocycloheptenes; Dizocilpine Maleate; Excitatory Amino Acid Antagonists; Female; Glutamic Acid; Ischemic Attack, Transient; Male; Receptors, N-Methyl-D-Aspartate; Receptors, Neurotransmitter

The neuroprotective effects of the non-competitive N-methyl-D-aspartate receptor antagonist (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine maleate (MK-801) have been evaluated in the gerbil hippocampus when the drug was administered i.p. at various times during and after a 5 min period of transient forebrain ischaemia, induced by bilateral common carotid artery occlusion. A single dose of 1, 3 or 10 mg/kg of MK-801 gave significant protection of hippocampal CA1 and CA2 pyramidal neurons when administered during the occlusion and up to 24 h following the period of ischaemia. A dose of 0.3 mg/kg was effective when administered during the occlusion period but gave no protection at 30 min or 2 h post-ischaemia. Experiments in which MK-801 was administered in repeated doses indicated that significant protection was achieved with 1 mg/kg of MK-801 repeated post-ischaemically and with 1 mg/kg MK-801 supplemented with repeated doses of 0.3 mg/kg of MK-801. However 0.3 mg/kg of MK-801 followed by repeated doses of 0.03 mg/kg administered post-ischaemically was not neuroprotective. These results indicate that MK-801 can protect hippocampal neurons from ischaemia-induced neuronal degeneration when it is administered up to 24 h after the insult. These data provide further evidence that therapeutic intervention in the post-ischaemic period can successfully prevent neurodegenerative events, and that the delayed degeneration of hippocampal neurons following an ischaemic insult occurs by an N-methyl-D-aspartate receptor-mediated process.

Topics: Animals; Dibenzocycloheptenes; Dizocilpine Maleate; Dose-Response Relationship, Drug; Female; Gerbillinae; Hippocampus; Ischemic Attack, Transient; Male; Nerve Degeneration; Time Factors

Ischemia may increase synaptic concentrations of glutamate, which may cause neuronal damage. Drugs that antagonize glutamate's effects may reduce this type of damage. MK-801, an N-methyl-D-aspartate receptor antagonist that readily enters the central nervous system, was evaluated in two focal central nervous system ischemia models: a multiple cerebral embolic model and a rabbit spinal cord ischemia model. When animals were treated five minutes after the onset of injury, MK-801 was effective in reducing ischemic damage in both models. In the multiple cerebral embolic model, the average dose of microspheres trapped in the brain increased from 344.8 +/- 51.4 micrograms (n = 29) in controls to 534 +/- 41.4 micrograms (n = 17) in the MK-801-treated group. Similarly, in the rabbit spinal cord ischemia model, the average ischemia duration increased from 28.9 +/- 1.7 minutes (n = 52) in controls to 50.6 +/- 3.9 minutes (n = 12) in the MK-801-treated group. These results suggest that this glutamate antagonist should be useful for the treatment of stroke.

Topics: Animals; Behavior, Animal; Dibenzocycloheptenes; Disease Models, Animal; Dizocilpine Maleate; Excitatory Amino Acid Antagonists; Intracranial Embolism and Thrombosis; Ischemia; Ischemic Attack, Transient; Male; Rabbits; Spinal Cord

Topics: Animals; Dibenzocycloheptenes; Dizocilpine Maleate; Humans; Ischemic Attack, Transient; Receptors, N-Methyl-D-Aspartate; Receptors, Neurotransmitter