2-3-dioxo-6-nitro-7-sulfamoylbenzo(f)quinoxaline and Ischemic-Attack--Transient

Topics: Animals; Brain Ischemia; Calcium; Ischemic Attack, Transient; Quinoxalines; Receptors, AMPA; Receptors, Glutamate; Time Factors

Under pathophysiological conditions, alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA) receptor activation is considered to play a key role in several disorders of the central nervous system. In the search for AMPA receptor antagonists, the synthesis and pharmacological characterization of a series of novel compounds that are structurally related to GYKI 52466 (1), a well-known selective noncompetitive AMPA receptor antagonist, was performed. In vitro, 2,3-dimethyl-6-phenyl-12H-[1,3]dioxolo[4,5-h]imidazo[1,2-c][2,3]benzodiazepine (ZK 187638, 14a) antagonized the kainate-induced currents in cultured hippocampal neurons with an IC(50) of 3.4 microM in a noncompetitive fashion. When tested in a clinically predictive rat model of acute ischemic stroke, this noncompetitive AMPA receptor antagonist significantly reduced brain infarction, indicating that it is neuroprotective after permanent focal cerebral ischemia.

Topics: Acute Disease; Animals; Benzodiazepines; Binding, Competitive; Brain Infarction; Cells, Cultured; Dioxoles; Hippocampus; In Vitro Techniques; Ischemic Attack, Transient; Kainic Acid; Male; Mice; Nerve Degeneration; Neuroprotective Agents; Patch-Clamp Techniques; Prosencephalon; Radioligand Assay; Rats; Rats, Inbred F344; Receptors, AMPA

The present study examined whether anti-inflammatory drugs can ameliorate the postponed neuronal damage which has been observed following treatment of ischemic animals with 2,3-dihydro-6-nitro-7-sulfamoyl-benz (F) quinoxaline (NBQX). Global cerebral ischemia was induced in male Wistar rats by four-vessel occlusion for 20 min. The animals were treated either with NBQX, rolipram, doxycycline or a combination of NBQX and rolipram or doxycycline. Four weeks after ischemia neuronal damage in the hippocampus was assessed. Treatment with NBQX or doxycycline did not affect ischemic neuronal damage whereas rolipram alone or combination of NBQX with either rolipram or doxycycline reduced neuronal damage. The present study shows that combining NBQX with an anti-inflammatory drug leads to long-lasting protection. These results suggest that inflammation contributes to the postponed neuronal damage following treatment with NBQX.

Topics: Animals; Anti-Bacterial Agents; Doxycycline; Encephalitis; Excitatory Amino Acid Antagonists; Ischemic Attack, Transient; Male; Phosphodiesterase Inhibitors; Quinoxalines; Rats; Rats, Wistar; Rolipram

This study investigated the ability of NBQX, an AMPA receptor antagonist, and cerestat, a NMDA receptor antagonist, to counteract neurological deficits and morphological damage induced by permanent occlusion of the left middle cerebral artery (MCAO model) in the rat. NBQX (3, 10, and 30 mg/kg, ip) injected at 10, 60, and 120 min postocclusion did not reduce the volume of infarct in the MCAO model of cerebral ischemia and had marginal effects on sensory dysfunctions (vibrissae stimulation and body proprioception) and no effects on motor dysfunctions (forelimb flexion and footfault test). Conversely, cerestat (0.3, 1, and 3 mg/kg, sc) injected at 10 and 120 min postocclusion significantly reduced the ischemic volume at the dose of 1 mg/kg, and, at the same dose, significantly attenuated behavioural deficits in the body proprioception and in the forelimb flexion tests.

Topics: Animals; Behavior, Animal; Brain; Cerebral Infarction; Excitatory Amino Acid Antagonists; Forelimb; Guanidines; Ischemic Attack, Transient; Male; Middle Cerebral Artery; Neuroprotective Agents; Physical Stimulation; Proprioception; Psychomotor Performance; Quinoxalines; Rats; Rats, Inbred F344; Vibrissae

The present study was undertaken to explore the possible neuroprotective effect of the selective alpha2-adrenoceptor agonist, dexmedetomidine in a rat model of focal cerebral ischemia. The effect of dexmedetomidine (9 microg kg(-1)) on infarct volume was assessed and compared to that of glutamate receptor antagonists cis-4(phosphonomethyl)-2-piperidine carboxylic acid (CGS-19755) (20 mg kg(-1)) or 2,3-dihydro-6-nitro-7-sulfamoyl-benzo(F)quinoxaline (NBQX) (50 mg kg(-1)). Dexmedetomidine decreased total ischemic volume by 40% in the cortex (P<0.05) compared to NaCl-treated control rats, whereas NBQX reduced the infarct by 73% in the cortex (P<0.001) and by 43% in the striatum (P<0.01). Dexmedetomidine infusion was associated with some minor degree of hyperglycemia and hypotension. Drug-induced kidney changes were only seen in NBQX-treated rats. These results suggest that dexmedetomidine reduced ischemic volume despite causing a minor increase in blood glucose concentrations and hypotension. Its neuroprotective efficacy was better than that produced by CGS-19775, and dexmedetomidine was safer with respect to kidney toxicity when compared to NBQX.

Topics: Adrenergic alpha-Agonists; Animals; Arterial Occlusive Diseases; Body Weight; Cerebral Arteries; Cerebral Cortex; Cerebral Infarction; Corpus Striatum; Excitatory Amino Acid Antagonists; Imidazoles; Ischemic Attack, Transient; Male; Medetomidine; Neuroprotective Agents; Pipecolic Acids; Quinoxalines; Rats; Rats, Wistar

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

The neuroprotective activity of the non-competitive alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) antagonist GYKI-52466 (1-[4-aminophenyl]-4-methyl-7,8-methylene-dioxy-5H-2,3-benzodia zep ine HCI; EGIS-8159) was studied in the gerbil bilateral carotid occlusion (BCO) model of global ischemia. Drug effect on hippocampal CA1 neuronal loss, hypermotility, and cognitive deficit (decrease in spontaneous alternation (SA) behaviour in the Y-maze) induced by 5-min or 3-min BCO were measured. GYKI-52466 was administered at 4 x 15 mg/kg intraperitoneal (i.p.) doses 30, 45, 60, and 75 min following surgery. The competitive AMPA antagonist NBQX (2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo(F)-quinoxaline) applied at 3 x 30 mg/kg i.p. doses 60, 70, and 85 min after reperfusion was also tested for comparison. Both compounds showed weak and non-significant effects on 5-min BCO-induced changes in all the three variables. However, following 3-min ischemia GYKI-52466 and NBQX produced significant inhibition (49% and 48%, respectively) on CA1 cell loss. Moreover, GYKI-52466, but not NBQX, significantly inhibited the 3-min ischemia induced hypermotility and decrease in SA. At their neuroprotective doses, both compounds caused long-lasting (min. 8 h) hypothermia in gerbils. GYKI-52466 induced much higher decrease in body temperature (6 degrees C at peak level) than NBQX did (2 degrees C at peak level). Administration of 4 x 10 mg/kg i.p. chlorpromazine to gerbils 15 min before and 0, 15, and 30 min after 3-min BCO resulted in considerable hypothermia (5.5 degrees C peak effect, 8 h duration), but no protective action of the compound on CA1 cell loss and hypermotility was observed. However, chlorpromazine inhibited the ischemia-induced cognitive impairment. The results suggest that drug-induced hypothermia may differentially influence the histological and the behavioural outcomes of ischemic intervention.

Topics: Animals; Anti-Anxiety Agents; Benzodiazepines; Body Temperature; Chlorpromazine; Excitatory Amino Acid Antagonists; Gerbillinae; Ischemic Attack, Transient; Male; Maze Learning; Motor Activity; Neuroprotective Agents; Quinoxalines; Receptors, AMPA; Time Factors

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

Excitatory amino acids may promote microtubular proteolysis observed in ischemic neuronal degeneration by calcium-mediated activation of calpain, a neutral protease. We tested this hypothesis in an animal model of focal cerebral ischemia without reperfusion. Spontaneously hypertensive rats were treated with 2, 3-dihydroxy-6-nitro-7-sulfamoyl-benzo-(F)quinoxaline (NBQX), a competitive antagonist of the neuronal receptor for alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA), or cis-4-[phosphono-methyl]-2-piperidine carboxylic acid (CGS 19755), a competitive antagonist of the N-methyl-d-aspartate (NMDA) receptor. After treatment, all animals were subjected to permanent occlusion of the middle cerebral artery for 6 or 24 h. Infarct volumes measured in animals pretreated with CGS 19755 after 24 h of ischemia were significantly smaller than those quantified in ischemic controls. Rats pretreated with NBQX showed partial amelioration of cytoskeletal injury with preserved immunolabeling of microtubule-associated protein 2 (MAP 2) at 6 and 24 h and reduced accumulation of calpain-cleaved spectrin byproducts only at 6 h. Prevention of cytoskeletal damage was more effective after pretreatment with CGS 19755, as shown by retention of MAP 2 immunolabeling and significant restriction of calpain activity at both 6 and 24 h. Preserved immunolabeling of tau protein was observed at 6 and 24 h only in animals pretreated with CGS 19755. Western analysis performed on ischemic cortex taken from controls or rats pretreated with either NBQX or CGS 19755 suggested that loss of tau protein immunoreactivity was caused by dephosphorylation, rather than proteolysis. These results demonstrate a crucial link between excitotoxic neurotransmission, microtubular proteolysis, and neuronal degeneration in focal cerebral ischemia.

Topics: Animals; Blotting, Western; Calpain; Cerebral Infarction; Cytoskeleton; Excitatory Amino Acid Antagonists; Immunohistochemistry; Ischemic Attack, Transient; Male; Microtubule-Associated Proteins; Pipecolic Acids; Quinoxalines; Rats; Rats, Inbred SHR; Receptors, Glutamate; Spectrin; Synaptic Transmission; tau Proteins

Nitric oxide formed in vivo in the rat brain regions of hippocampus, striatum, neocortex and cerebellum was spin trapped and measured ex vivo by cryogenic electron paramagnetic resonance spectroscopy. In non-ischemic control animals the rate of nitric oxide (NO) formation in the individual brain regions ranged from 15 to 42 pmol.g-1.min-1. During exposure to global ischemia for 7 min the generation of NO increased in all parts of the brain. In the hippocampus the rate of NO formation during ischemia increased by 6-fold from a control rate of 19 pmol.g-1.min-1. This increase was attenuated 47% by pretreatment with the NO synthase antagonist 7-nitroindazole, whereas pretreatment with the non-NMDA receptor anatogonist NBQX and the Ca2+ channel blocker NS638 did not influence the NO formation. The data show that short-duration ischemia elicits a significant, NO-synthase-dependent formation of NO in all brain regions.

Topics: Analysis of Variance; Animals; Benzimidazoles; Brain; Calcium Channel Blockers; Electron Spin Resonance Spectroscopy; Enzyme Inhibitors; Gerbillinae; Hippocampus; Indazoles; Ischemic Attack, Transient; Male; Nitric Oxide; Nitric Oxide Synthase; Organ Specificity; Quinoxalines; Rats; Rats, Wistar; Receptors, N-Methyl-D-Aspartate; Reference Values

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

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

The new non-NMDA (N-methyl-D-aspartate) receptor antagonist NBQX (2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo(F)quinoxaline) has previously been shown to exert a neuroprotective effect in animal models of cerebral ischemia when administered in the post-ischemic phase. In this investigation the effect of NBQX on acidosis and energy recovery in early reperfusion after 10 min of transient forebrain ischemia with the 2-vessel occlusion model in the rat was studied with 31P NMR spectroscopy. In the intervention group the animals received a bolus dose of NBQX 30 mg.kg-1 i.v. at the start of reperfusion. 31P NMR spectroscopy was used to measure intracellular pH, ATP and phosphocreatine continuously in-vivo during, and after, the ischemic event. The recovery of high energy phosphates and pH was followed during 30 min of reperfusion. Pre-ischemic levels of phosphocreatine were reached after approximately 9-10 min in both groups. Although a slight improvement could be seen in the intervention group there was no significant difference in the rate of recovery between the two groups. ATP reached 90% of preischemic levels after about 8 min without significant difference between the two groups. With respect to the recovery of intracellular pH, no difference could be shown. Our results do not contradict previously published results, but suggest that the potential protective effect of NBQX is not mediated through improved recovery of energy metabolism in early reperfusion.

Topics: Acidosis; Adenosine Triphosphate; Animals; Energy Metabolism; Hydrogen-Ion Concentration; Ischemic Attack, Transient; Magnetic Resonance Spectroscopy; Male; Phosphocreatine; Phosphorus; Prosencephalon; Quinoxalines; Rats; Rats, Wistar; Receptors, AMPA; Reperfusion; Time Factors

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

Two groups of rats were subjected to 12 min of global cerebral ischemia and 6 days recirculation using the four-vessel occlusion model with hypotension and then treated with the alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) antagonist NBQX [2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo (F) quinoxalinedione (Honoré et al. 1988]. One group was used for routine and quantitative histology and immunostaining for glial fibrillary acidic protein (GFAP). The second group was subjected to autoradiographic studies of regional cerebral protein synthesis, with special emphasis on the hippocampus, the frontal cortex, and the thalamus. It was found that neuroprotective treatment with NBQX normalized cerebral protein synthesis rate (CPSR) in all investigated regions 6 days after ischemia. In untreated ischemic animals CPSR was normalized in all regions except for the CA3 and thalamus, where it had increased by 29% and 41%, respectively. Treatment of controls with NBQX had no effect on CPSR after 6 days. The histological investigations revealed that NBQX did not protect vulnerable cells in the dentate hilus and the reticular thalamic nucleus (RTN). In these regions reactive astrocytosis visualized by GFAP immunostaining was equally pronounced in both ischemic and NBQX-treated animals, and most neurons in the RTN were eosinophilic. The 80-100% pyramidal neuron loss in CA1 was accompanied by a high degree of reactive astrocytosis, whereas the NBQX-treated animals showed no signs of astrocytosis in this region. The ischemic CA1 pyramidal layer was also massively invaded by microglia.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; Animals; Astrocytes; Autoradiography; Brain; Frontal Lobe; Hippocampus; Ischemic Attack, Transient; Male; Methionine; Nerve Tissue Proteins; Neurons; Pyramidal Tracts; Quinoxalines; Rats; Rats, Wistar; Sulfur Radioisotopes; Thalamus

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

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

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

The cerebroprotective action of non-NMDA receptor blockade has been assessed in a model of transient global ischaemia using NBQX, 2,3-dihydro-6-nitro-7-sulphamoyl-benzo(F)quinoxaline, and GYKI 52466, 1-(amino-phenyl)-4-methyl-7,8-methylendioxy-5H-2,3-benzodiazepine. HCl. In Wistar rats, prior cauterisation of the vertebral arteries was followed by occlusion of the common carotid arteries for 20 min, with a 7 day survival period before histological evaluation. NBQX, 40 mg/kg, or GYKI 52466, 40 mg/kg, was administered intravenously starting directly after the end of carotid occlusion and ending 3 h later. Both compounds produced significant protection against selective cell loss in the striatum and cortex. Less consistent changes were seen in the hippocampus; protection by NBQX was significant in CA3 but neither compound produced significant protection in CA1. This pattern of protection is interpreted in terms of a blockade of glutamate's action at non-NMDA receptors limited to the initial 3 h of reperfusion.

Topics: Animals; Anti-Anxiety Agents; Benzodiazepines; Cell Death; Cerebral Cortex; Corpus Striatum; Excitatory Amino Acid Antagonists; Glutamic Acid; Ischemic Attack, Transient; Male; Quinoxalines; Rats; Rats, Inbred Strains

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

Normothermic rats with 12 min, complete cerebral ischemia were treated with the AMPA antagonist 2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo (F) quinoxalinedione (NBQX) [10], which prevents CA1 pyramidal neuron loss. Twenty hours after ischemia, cerebral protein synthesis rate (CPSR) was measured autoradiographically using [35S]methionine. Ischemia caused a 38% decrease of CPSR in CA1, and postischemic treatment with NBQX caused a 66% decrease in this region. Also treatment with NBQX alone resulted in a decrease (22% in CA1) of the CPSR. Since some evidence exists that the neuroprotective effect of NBQX is related to blockade of the fast AMPA-mediated transmission, the further decrease of the postischemic CPSR in CA1 could be a mere side effect.

Topics: alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; Animals; Autoradiography; Brain; Ibotenic Acid; Ischemic Attack, Transient; Male; Methionine; Nerve Tissue Proteins; Neurons; Organ Specificity; Quinoxalines; Rats; Rats, Wistar; Sulfur Radioisotopes

We examined the effect of an AMPA (alpha-amino-3-hydroxy-5-methyl-4-isoxazole) antagonist, 2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo (F) quinoxaline (NBQX), on rat cerebellar Purkinje cell loss and hippocampal pyramidal CA1 cell loss, after 10 minutes of global cerebral ischemia. NBQX was given intraperitoneally in a dose of 30 mg kg-1 at the end of ischemia, and 10 and 25 minutes later. Rats subjected to ischemia without post-ischemic administration of NBQX served as controls. Four days after ischemia the cerebellar Purkinje cell density was higher and the density of acidophilic (dead) Purkinje cells lower in the NBQX treated animals compared with the control animals (p = 0.01 and p less than 0.005 respectively). There was partial to total loss of pyramidal neurons in the CA1 region of the dorsal hippocampus in control animals, but no CA1 pyramidal neuron loss in the NBQX treated animals (p = 0.001).

Topics: alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; Animals; Cell Death; Ibotenic Acid; Ischemic Attack, Transient; Male; Purkinje Cells; Quinoxalines; Rats; Rats, Wistar

The neuroprotective effects of NBQX, a selective antagonist for the AMPA/kainate subtype of excitatory amino acid receptors, were investigated in a rat focal ischaemia model, involving permanent occlusion of the left middle cerebral artery (MCA). NBQX (3, 10 or 30 mg/kg) was administered i.v. immediately after MCA occlusion and again 1 h later. The highest dose of NBQX (2 x 30 mg/kg) gave significant protection against hemispheric (24%) and cortical (27%) ischaemic damage. The lower doses of NBQX (2 x 3 or 2 x 10 mg/kg) were ineffective. No protection was seen against caudate damage for any of the doses of NBQX tested. NBQX has a t1/2 of 30 min, therefore, a second experiment was done in which a dose of 30 mg/kg was given as an i.v. bolus followed immediately by an infusion of 10 mg/kg/h for 4 h, dosing was started immediately after MCA occlusion. This dosing regimen resulted in a mean plasma level over the 4 h of 17 micrograms/ml, and significant protection against the volume of hemispheric (29%) and cortical (35%) ischaemic damage, which was slightly better than that achieved with two bolus doses of 30 mg/kg. Once again no protection was seen against caudate damage. We conclude that NBQX, an AMPA/kainate antagonist was neuroprotective in a focal ischaemia model in the rat.

Topics: Analysis of Variance; Animals; Blood Pressure; Disease Models, Animal; Dose-Response Relationship, Drug; Infusions, Intravenous; Ischemic Attack, Transient; Male; Quinoxalines; 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

The potent and selective AMPA receptor antagonist NBQX was tested for cytoprotective properties in an adult rat model of transient focal neocortical ischemia. Nineteen spontaneously hypertensive rats sustained 2 h of middle cerebral artery occlusion, followed by 22 h of recirculation. Ninety minutes following the onset of ischemia, at the time of, and 30 min following reperfusion, they received i.p. injections of either saline (n = 10) or 30 mg kg-1 of NBQX (n = 9). Saline-treated rats had a mean volume of neocortical infarction ( +/- s.d.) of 181 +/- 31 mm3, while NBQX-treated rats sustained significantly less damage, 125 +/- 19 mm3 (p less than 0.001). Regional cerebral blood flows during ischemia and reperfusion were not affected by the drug. We suggest that the AMPA receptor may play an important role in ischemic cerebral infarction.

Topics: Animals; Blood Pressure; Carbon Dioxide; Cerebral Infarction; Cerebrovascular Circulation; Ischemic Attack, Transient; Male; Oxadiazoles; Oxygen; Partial Pressure; Quinoxalines; Rats; Rats, Inbred SHR; Receptors, AMPA; Receptors, Neurotransmitter

The cytoprotective effect of NBQX, a selective AMPA receptor antagonist, was tested following 10 min of severe forebrain ischemia using the 4-vessel occlusion model. Immediately, and at 15 and 30 min following reperfusion, adult Wistar rats received intraperitoneal injections of either saline (n = 5), 1 mg lithium chloride (n = 17) or 30 mg/kg of the lithium salt of NBQX (n = 18). In saline-treated animals 82 +/- 12% of CA1 hippocampal neurons were lost. Of those treated with lithium 70 +/- 23% were injured, while those given NBQX sustained only 40 +/- 34% CA1 necrosis (P less than 0.01). Twelve of 18 NBQX-treated animals had less than 30% CA1 injury as compared with 1 of 17 lithium-treated animals. The AMPA receptor may play a more important role than the NMDA receptor in selective ischemic necrosis of hippocampal neurons.

Topics: Animals; Cell Death; Chlorides; Hippocampus; Ischemic Attack, Transient; Lithium; Lithium Chloride; Neurons; Quinoxalines; Rats; Rats, Inbred Strains; Receptors, AMPA; Receptors, Neurotransmitter; Reperfusion; Sodium Chloride

The neuroprotective effects of NBQX (2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo(f)quinoxaline) were assessed on hippocampal CA1 neuronal loss and locomotor hyperactivity following transient bilateral carotid artery occlusion (BCAO) in the gerbil. NBQX, a selective blocker of the AMPA glutamate receptor subtype, was injected 1 h after 5 or 10 min BCAO, or sham surgery. Both 5 and 10 min ischemia produced equivalent hyperactivity 3 days post ischemia and CA1 neuronal loss on Day 4, while activity was unchanged in the sham-operated group. NBQX protected from both hippocampal damage and post-ischemic hyperactivity. These results demonstrate that NBQX can protect from behavioral pathology induced by global cerebral ischemia.

Topics: Animals; Gerbillinae; Hippocampus; Ischemic Attack, Transient; Male; Motor Activity; Neurons; Pyramidal Tracts; Quinoxalines; Receptors, AMPA; Receptors, Neurotransmitter