2-3-dioxo-6-nitro-7-sulfamoylbenzo(f)quinoxaline and Brain-Ischemia

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

The present study aims to investigate the effect of noscapine (0.5-2.5 μM), an alkaloid from the opium poppy, on primary murine fetal cortical neurons exposed to oxygen-glucose deprivation (OGD), an in vitro model of ischemia.. Cells were transferred to glucose-free DMEM and were exposed to hypoxia in a small anaerobic chamber. Cell viability and nitric oxide production were evaluated by MTT assay and the Griess method, respectively.. The neurotoxicities produced by all three hypoxia durations tested were significantly inhibited by 0.5 μM noscapine. Increasing noscapine concentration up to 2.5 μM produced a concentration-dependent inhibition of neurotoxicity. Pretreatment of cells with MK-801 (10 μM), a non-competitive NMDA antagonist, and nimodipine (10nM), an L-type Ca(2+) channel blockers, increased cell viability after 30 min OGD, while the application of NBQX (30 μM), a selective AMPA-kainate receptor antagonist partially attenuated cell injury. Subsequently, cells treated with noscapine in the presence of thapsigargin (1 μM), an inhibitor of endoplasmic reticulum Ca(2+) ATPases. After 60 min OGD, noscapine could inhibit the cell damage induced by thapsigargin. However, noscapine could not reduce cell damage induced by 240 min OGD in the presence of thapsigargin. Noscapine attenuated nitric oxide (NO) production in cortical neurons after 30 min OGD.. We concluded that noscapine had a neuroprotective effect, which could be due to its interference with multiple targets in the excitotoxicity process. These effects could be mediated partially by a decrease in NO production and the modulation of intracellular calcium levels.

Topics: Animals; Brain Ischemia; Cell Survival; Dizocilpine Maleate; Dose-Response Relationship, Drug; Glucose; Hypoxia; Mice; Neurons; Neuroprotective Agents; NG-Nitroarginine Methyl Ester; Nimodipine; Nitric Oxide; Noscapine; Primary Cell Culture; Quinoxalines; Thapsigargin

Lipocalin-type prostaglandin D synthase (L-PGDS) is a member of the lipocalin superfamily and a secretory lipid-transporter protein, which binds a wide variety of hydrophobic small molecules. Here we show the feasibility of a novel drug delivery system (DDS), utilizing L-PGDS, for poorly water-soluble compounds such as diazepam (DZP), a major benzodiazepine anxiolytic drug, and 6-nitro-7-sulfamoylbenzo[f]quinoxaline-2,3-dione (NBQX), an α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor antagonist and anticonvulsant. Calorimetric experiments revealed for both compounds that each L-PGDS held three molecules with high binding affinities. By mass spectrometry, the 1:3 complex of L-PGDS and NBQX was observed. L-PGDS of 500μM increased the solubility of DZP and NBQX 7- and 2-fold, respectively, compared to PBS alone. To validate the potential of L-PGDS as a drug delivery vehicle in vivo, we have proved the prospective effects of these compounds via two separate delivery strategies. First, the oral administration of a DZP/L-PGDS complex in mice revealed an increased duration of pentobarbital-induced loss of righting reflex. Second, the intravenous treatment of ischemic gerbils with NBQX/L-PGDS complex showed a protective effect on delayed neuronal cell death at the hippocampal CA1 region. We propose that our novel DDS could facilitate pharmaceutical development and clinical usage of various water-insoluble compounds.

Topics: Animals; Anti-Anxiety Agents; Anticonvulsants; Brain Ischemia; CA1 Region, Hippocampal; Diazepam; Disease Models, Animal; Drug Delivery Systems; Gerbillinae; Glutathione Transferase; Intramolecular Oxidoreductases; Lipocalins; Male; Mice; Pyramidal Cells; Quinoxalines; Recombinant Fusion Proteins; Solubility; Water

We characterized the differential effects of glycine at different levels in the induction of postischemic long-term potentiation, as well as in the neuronal damage induced by focal ischemia.. Whole-cell patch clamp recordings were obtained from rat hippocampal slice preparations. In vitro ischemia and postischemic long-term potentiation were induced by oxygen and glucose deprivation. In vivo ischemia was induced by transient middle cerebral artery occlusion.. In both in vitro and in vivo ischemia models, glycine at low level exerts deleterious effects in postischemic long-term potentiation and ischemic neuronal injury by modulation of the N-methyl-d-aspartate receptor coagonist site; whereas glycine at high level exerts neuroprotective effects by activation of glycine receptor and subsequent differential regulation of N-methyl-d-aspartate receptor subunit components.. Our results provide a molecular basis for the dual roles of glycine in ischemic injury through distinct mechanisms, and they suggest that glycine receptors could be a potential target for clinical treatment of stroke.

Topics: 2-Amino-5-phosphonovalerate; Animals; Brain Ischemia; Dose-Response Relationship, Drug; Glucose; Glycine; Hippocampus; Hypoxia, Brain; Infarction, Middle Cerebral Artery; Long-Term Potentiation; Male; Patch-Clamp Techniques; Quinoxalines; Rats; Rats, Sprague-Dawley; Receptors, Glycine; Receptors, N-Methyl-D-Aspartate; Stereotaxic Techniques; Viruses

Dark neurons have plagued the interpretation of brain tissue sections, experimentally and clinically. Seen only when perturbed but living tissue is fixed in aldehydes, their mechanism of production is unknown. Since dark neurons are seen in cortical biopsies, experimental ischemia, hypoglycemia, and epilepsy, we surmised that glutamate release and neuronal transmembrane ion fluxes could be the perturbation leading to dark neuron formation while the fixation process is underway. Accordingly, we excised biopsies of rat cortex to simulate neurosurgical production of dark neurons. To ascertain the role of glutamate, blockade of N-methyl-D-aspartate (NMDA) and non-NMDA receptors was done prior to formaldehyde fixation. To assess the role of transmembrane sodium ion (and implicitly, water) fluxes, tetraethylammonium (TEA) was used. Blockade of NMDA receptors with MK-801 and non-NMDA receptors with the quinoxalinediones (CNQX and NBQX) abolished dark neuron formation. More delayed exposure of the tissue to the antagonist, CNQX, by admixing it with the fixative directly, allowed for some production of dark neurons. Aminophosphonoheptanoate (APH), perhaps due to its polarity, and TEA, did not prevent dark neurons, which were abundant in control formaldehyde fixed material unexposed to either receptor or ion channel antagonists. The results demonstrate a role for the pharmacologic subtypes of glutamate receptors in the pathogenetic mechanism of dark neuron formation. Our results are consistent with the appearance of dark neurons in biopsy where the cerebral cortex has been undercut, and rendered locally ischemic and hypoglycemic, as well as in epilepsy, hypoglycemia, and ischemia, all of which lead to glutamate release. Rather than a pressure-derived mechanical origin, we suggest that depolarization, glutamate release or receptor activation are more likely mechanisms of dark neuron production.

Topics: 6-Cyano-7-nitroquinoxaline-2,3-dione; Animals; Artifacts; Biopsy; Brain Ischemia; Cerebral Cortex; Dizocilpine Maleate; Epilepsy; Excitatory Amino Acid Antagonists; Glutamic Acid; Hypoglycemia; Male; Neurons; Potassium Channel Blockers; Quinoxalines; Rats; Rats, Wistar; Receptors, Glutamate; Receptors, N-Methyl-D-Aspartate; Tetraethylammonium

Herein, we report an extensive investigation of the neuroprotective effects of the compound (Z)-alpha-[2-thiazol-2-yl)imidazol-4-yl]-N-tert-butylnitrone (S34176) and the prototypic nitrone alpha-phenyl-N-tert-butylnitrone (PBN), in different in vivo paradigms of neuronal degeneration. Administration of S34176 (75 mg/kg i.p.) 30 min before transient (10 min) global ischaemia in Wistar rats significantly prevented delayed neuronal cell death in the hippocampal CA1 area 7 days post-ischaemia (24% vs. 73% in ischaemia control; P<0.05) whereas PBN was inactive under similar conditions. Furthermore, oral administration of S34176 (30 mg/kg) 60 min before and during (1 x 30 mg/kg p.o.) 6 days post-ischaemia, in combination with an acute post-ischaemia sub-protective dose (3 x 10 mg/kg i.p.) of the glutamate receptor antagonist, 1,2,3,4-tetrahydro-6-nitro-2,3-dioxo-benzo[f]quinoxaline-7-sulfonamide (NBQX), resulted in an increased neuroprotective action (29% cell loss in drug-treated vs. 84% in ischaemia control P<0.001) compared to either compound alone. S34176 (20 mg/kg i.p.) also partially prevented kainic acid-induced neuronal cell death at 7 days post-exposure in the CA1 (41% in drug-treated vs. 74% for kainate-treated controls; P<0.01) and CA3 hippocampal region (22% vs. 53%; P<0.01). Under similar conditions, S34176 administered orally (40 mg/kg) produced a more marked protection against kainate-induced neuronal cell loss in the CA1 (13% in drug-treated vs. 82%; P<0.001) and CA3 areas (10% vs. 52%; P<0.001). Sub-chronic oral administration of S34176 (10 mg/kg) also partially reduced kainate-induced hippocampal cell death in the CA1 (53% vs. 77%; P<0.01) and CA3 (23% vs. 53%; P<0.01) areas. Dopamine depletion in the striatum of C57BL/6 mice induced by systemic D-methamphetamine injection was significantly reduced by S34176 (40+/-5% vs. 11.5+/-8%; P<0.001) (150 mg/kg i.p.) whereas PBN was inactive under similar conditions. S34176 represents a new centrally acting nitrone-based radical scavenger with neuroprotective properties in in vivo models of delayed neuronal cell death, and supports the therapeutic potential of this class of compound for the treatment of cerebral pathologies implicating chronic neurodegeneration.

Topics: Animals; Brain Ischemia; Cell Survival; Corpus Striatum; Dopamine; Free Radical Scavengers; Hippocampus; Imidazoles; Kainic Acid; Male; Methamphetamine; Mice; Mice, Inbred C57BL; Neurons; Neuroprotective Agents; Nitrogen Oxides; Quinoxalines; Rats; Rats, Wistar

Alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor antagonists have been shown to have neuroprotective effects in stroke models and although clinical trials with some agents are still ongoing, published results have not been favourable. We therefore wished to compare the effects of GYKI 52466, GYKI 53405, EGIS-8332 and EGIS-10608, non-competitive AMPA receptor antagonists with homophthalazine chemical structures, in standard animal stroke models with effects in a neurodegenerative model--excitoxicity in newborn mice. All compounds inhibited the S-AMPA-induced spreading depression in the chicken retina, in vitro, and were potent anticonvulsants against maximal electroshock in mice, in vivo. The AMPA receptor antagonists prevented domoate-induced cell death of motoneurons, in vitro, and reduced infarct size in a dose-dependent manner in the permanent middle cerebral artery occlusion model in mice, in vivo. In newborn mice (P5, histopathology at P10), local injection of the AMPA receptor agonist S-bromo-willardiine at day 5 after birth induced cortical damage and white matter damage, which was reduced in a dose-dependent manner by the AMPA receptor antagonists. EGIS 10608 was a very powerful receptor antagonist of white matter damage. In contrast, GYKI 52466 did not antagonize cortical and white matter damage induced by ibotenic acid. These models allow quantification of the effects of AMPA receptor antagonists in vitro and in vivo.

Topics: Animals; Animals, Newborn; Anticonvulsants; Benzodiazepines; Brain; Brain Ischemia; Cell Survival; Chickens; Cortical Spreading Depression; Disease Models, Animal; Dose-Response Relationship, Drug; Electroshock; Excitatory Amino Acid Antagonists; Infarction, Middle Cerebral Artery; Male; Mice; Mice, Inbred Strains; Motor Neurons; Nerve Degeneration; Quinoxalines; Rats; Rats, Sprague-Dawley; Receptors, AMPA; Retina; Seizures; Stroke

Although stroke is a major cause of death and disability in the elderly, the inhibitory effects of neuroprotectants in acute stroke have been investigated using experimental cerebral ischemic models of young animals. Recent clinical trials have found that few neuroprotectants are effective. These observations indicate that effects in the clinical setting do not always reflect data from young animals. Thus, we compared the effects of the NMDA receptor antagonist MK-801 and of the AMPA receptor antagonist NBQX [2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo(F)quinixaline] on ischemic cerebral damage in the photothrombosis model of aged and young rats. MK-801 administered immediately after MCA occlusion significantly (P<0.05) reduced the extent of cerebral damage in young, but not in aged, rats and the effects of NBQX were similar. In separate experiments, we evaluated brain damage after microinjecting NMDA or kainic acid into the cortex using a stereotaxic apparatus. We found no significant differences in focal cerebral damage caused by NMDA between young and aged rats. On the other hand, kainic acid caused all of the aged rats tested to die, but none of the young rats. Our observations indicate that NMDA and AMPA receptor antagonists are less effective in aged, than in young, rats and that cerebral damage by receptor agonists depends on the type of receptor, such as NMDA and AMPA.

Topics: Aging; Animals; Brain Ischemia; Cerebral Infarction; Disease Models, Animal; Dizocilpine Maleate; Excitatory Amino Acid Antagonists; Infarction, Middle Cerebral Artery; Kainic Acid; Male; Nerve Degeneration; Neurons; Neuroprotective Agents; Quinoxalines; Rats; Rats, Sprague-Dawley; Receptors, AMPA; Receptors, N-Methyl-D-Aspartate; Telencephalon

Neurons and glia reacting to ischemic injury exhibit delayed expression of heat shock proteins (HSPs). We tested the hypothesis that glutamate receptor antagonists alter neuronal and glial activation during focal cerebral ischemia, as shown by spatio-temporal changes in HSP immunoreactivity. Rats underwent focal ischemia by permanent occlusion of the middle cerebral artery. All animals were pre-treated with NBQX (30 mg kg-1), a competitive antagonist of the AMPA/kainate receptor, or CGS-19755 (10 mg kg-1), a competitive NMDA receptor antagonist, and euthanatized after 6 or 24 h of ischemia to demonstrate regional immunoreactivity of HSP-72 or 32 in brain. Neurons immunolabeled for HSP-72 appeared in the penumbral region adjacent to the infarct at 24 h and increased in number and distribution after pretreatment with NBQX or CGS-19755. Immunolabeling for HSP-32 revealed that pre-treatment with CGS-19755 caused ramified glia to infiltrate the ischemic cortex at 6 h, a pattern that was not seen in ischemic controls until 24 h. Blockade of the NMDA or AMPA/kainate receptor modulates cellular stress responses in both neurons and glia within the developing infarct. We conclude that early, rather than delayed, expression of HSP-32 is a sensitive indicator of glial activation induced specifically by CGS-19755.

Topics: Animals; Brain Ischemia; Excitatory Amino Acid Antagonists; Heat-Shock Proteins; Heme Oxygenase (Decyclizing); Heme Oxygenase-1; HSP72 Heat-Shock Proteins; Infarction, Middle Cerebral Artery; Male; Pipecolic Acids; Quinoxalines; Rats; Rats, Inbred SHR

In this study, we investigated whether the novel neuroprotective compound dimethyl-[2-[2-(3-phenyl-[1,2,4]oxadiazol-5-yl)-phenoxy]-ethyl]-amine hydrochloride, BIIR 561 CL, a combined non-competitive antagonist of AMPA receptors and blocker of voltage-gated Na+ channels, is protective in a rat model of severe global ischaemia. BIIR 561 CL administered immediately after 10 min of ischaemia (occlusion of both carotid arteries plus reduction of arterial blood pressure to 38-40 mm Hg) significantly reduced hippocampal damage at 4 x 26.8 mg/kg (subcutaneous injections). The competitive AMPA receptor antagonist 2,3-dihydro-6-nitro-7-sulfamoyl-benz(F)quinoxaline, NBQX, was used as a reference compound and was protective at 3x30 mg/kg (intraperitoneal and/or subcutaneous administration). BIIR 561 CL significantly reduced the ischaemia-induced premature mortality from 33.6% in the controls to 14.3%, whereas NBQX treatment had no statistically significant effect.Thus, BIIR 561 CL could be shown to reduce hippocampal damage and premature mortality in a model of severe global ischaemia. A compound with these properties might be an interesting candidate for the treatment of disorders related to global cerebral ischaemia in man.

Topics: Animals; Brain Ischemia; Disease Models, Animal; Dose-Response Relationship, Drug; Hippocampus; Male; Neuroprotective Agents; Oxadiazoles; Quinoxalines; Rats; Rats, Wistar; Receptors, AMPA; Sodium Channel Blockers; Survival Rate

A simple and reproducible animal model of global ischemia, induced by decapitation in 30-day-old Wistar rats, has been developed. It allows to perform electrophysiological analysis of the postischemic reperfusion period in the brain slices. Periods of ischemia up to 40 min increase population spikes measured in the CA1 area of the hippocampus during 2-5 h of reperfusion. Thus after 30-min decapitation-induced ischemia (at t(ischem)=25 degrees C), the mean amplitude of the recorded maximum orthodromic population spikes was 159% of the control obtained in the non-ischemic animals. Longer ischemic episodes result in the depression of the population spikes. After 2 h of ischemia, the amplitude of population spikes was about 89% of control. After 3 h of decapitation ischemia, the neurons could not be reactivated. The duration of ischemic episode needed for the irreversible depression of the electrical activity of the brain neurons drastically depends on the temperature at which the ischemic brain is maintained. Thus, only 2 h were needed at 30 degrees C as compared to nearly 3 h at 25 degrees C. We have found that intraperitoneal injection of neuroprotectors which precedes decapitation enables reactivation of the post-ischemic neurons even after very long periods of global ischemia. Thus, MK-801, a non-competitive NMDA receptors antagonist, or NBQX, a blocker of AMPA receptors, administrated 15 min before the long-term (90 min) decapitation ischemia (30 degrees C), induced dose-dependent recovery of population spike with ED(50) values 0.2 mg/kg and 3 mg/kg respectively. Our results demonstrate that, in spite of the high vulnerability of hippocampal neurons to hypoxia and ischemia, their electrical activity can be restored after prolonged (more then 1 h) decapitation ischemia. Administration of NMDA or AMPA antagonists enhances recovery.

Topics: Action Potentials; Animals; Brain Ischemia; Dizocilpine Maleate; Dose-Response Relationship, Drug; Excitatory Amino Acid Antagonists; Hippocampus; Neurons; Neuroprotective Agents; Quinoxalines; Rats; Rats, Wistar; Time Factors

The extracellular glutamate concentration ([glu](o)) rises during cerebral ischemia, reaching levels capable of inducing delayed neuronal death. The mechanisms underlying this glutamate accumulation remain controversial. We used N-methyl-D-aspartate receptors on CA3 pyramidal neurons as a real-time, on-site, glutamate sensor to identify the source of glutamate release in an in vitro model of ischemia. Using glutamate and L-trans-pyrrolidine-2,4-dicarboxylic acid (tPDC) as substrates and DL-threo-beta-benzyloxyaspartate (TBOA) as an inhibitor of glutamate transporters, we demonstrate that energy deprivation decreases net glutamate uptake within 2-3 min and later promotes reverse glutamate transport. This process accounts for up to 50% of the glutamate accumulation during energy deprivation. Enhanced action potential-independent vesicular release also contributes to the increase in [glu](o), by approximately 50%, but only once glutamate uptake is inhibited. These results indicate that a significant rise in [glu](o) already occurs during the first minutes of energy deprivation and is the consequence of reduced uptake and increased vesicular and nonvesicular release of glutamate.

Topics: 2-Amino-5-phosphonovalerate; Amino Acid Transport System X-AG; Animals; Aspartic Acid; ATP-Binding Cassette Transporters; Biological Transport; Brain Ischemia; Dicarboxylic Acids; Excitatory Amino Acid Antagonists; Glutamic Acid; Hippocampus; Kinetics; Membrane Potentials; N-Methylaspartate; Neurotransmitter Uptake Inhibitors; Organ Culture Techniques; Patch-Clamp Techniques; Pyrrolidines; Quinoxalines; Rats

We have evaluated the neuroprotective effects of the decahydroisoquinoline LY377770, a novel iGlu5 kainate receptor antagonist, in two models of cerebral ischaemia. Global ischaemia, induced in gerbils by bilateral carotid artery occlusion (BCAO) for 5 min, produced a large increase in locomotor activity at 96 hr post-occlusion and a severe loss of CA1 cells in the hippocampus histologically at 120 hr post-occlusion. LY377770 (80 mg/kg i.p. 30 min before or 30 min after BCAO followed by 40 mg/kg i.p. administered at 3 and 6 hr after the initial dose) attenuated the ischaemia-induced hyperactivity and provided (92%) and (29%) protection in the CA1 cells respectively. This protection was greater than that seen with maximally tolerated doses of other glutamate receptor antagonists (CGS19755, CPP, MK-801, ifenprodil, eliprodil, HA-966, ACEA1021, L701,324, NBQX, LY293558, GYKI52466 and LY300164). Focal ischaemia was induced by infusing 200 pmol of endothelin-1 (Et-1) adjacent to the middle cerebral artery and LY377770 was administered at 80 mg/kg i.p. immediately, 1 or 2 hr post-occlusion followed by 40 mg/kg i.p. 3 and 6 hr after the first dose. The infarct volume, measured 72 hr later, was reduced by LY377770 when given immediately (P<0.01), at 1 hr (P<0.05) but not significantly at 2 hr post-occlusion. Reference compounds, LY293558 (20 mg/kg i.p. and then 10 mg/kg as above) and MK-801 (2.5 mg/kg i.p. ), both administered immediately post-occlusion produced significant (P<0.05) but somewhat less neuroprotection. In parallel microdialysis studies, LY377770 (75 mg/kg i.p.) attenuated ischaemia-induced increases in extracellular levels of glutamate, but not of dopamine. In conclusion, these results indicated that iGlu5 kainate receptors play a central role in ischaemic brain damage following global and focal cerebral ischaemia. LY377770 is a novel, soluble, systemically active iGlu5 antagonist with efficacy in global and focal ischaemia, even when administered post-occlusion. LY377770 may therefore be useful as a neuroprotectant in man.

Topics: Animals; Brain Ischemia; Carotid Stenosis; Cell Death; Dizocilpine Maleate; Excitatory Amino Acid Antagonists; Gerbillinae; Hippocampus; In Situ Nick-End Labeling; Isoquinolines; Male; Microdialysis; Motor Activity; Neuroprotective Agents; Quinoxalines; Rats; Rats, Sprague-Dawley; Rats, Wistar; Receptors, Kainic Acid; Tetrazoles

A prominent feature of cerebral ischemia is the excessive intracellular accumulation of both Na(+) and Ca(2+), which results in subsequent cell death. A large number of studies have focused on pathways involved in the increase of the intracellular Ca(2+) concentration [Ca(2+)](i), whereas the elevation of intracellular Na(+) has received less attention. In the present study we investigated the effects of inhibitors of different Na(+) channels and of the Na(+)/Ca(2+) exchanger, which couples the Na(+) to the Ca(2+) gradient, on ischemic damage in organotypic hippocampal slice cultures. The synaptically evoked population spike in the CA1 region was taken as a functional measure of neuronal integrity. Neuronal cell death was assessed by propidium iodide staining. The Na(+) channel blocker tetrodotoxin, and the NMDA receptor blocker MK 801, but not the AMPA/kainate receptor blocker NBQX prevented ischemic cell death. The novel Na(+)/Ca(2+) exchange inhibitor 2-[2-[4-(4-nitrobenzyloxy)phenyl]ethyl]isothiourea methanesulfonate (KB-R7943), which preferentially acts on the reverse mode of the exchanger, leading to Ca(2+) accumulation, also reduced neuronal damage. At higher concentrations, KB-R7943 also inhibits Ca(2+) extrusion by the forward mode of the exchanger and exaggerates neuronal cell death. Neuroprotection by KB-R7943 may be due to reducing the [Ca(2+)](i) increase caused by the exchanger.

Topics: Animals; Brain Ischemia; Cell Death; Culture Techniques; Dizocilpine Maleate; Electrophysiology; Hippocampus; Homeostasis; Hypoglycemia; Hypoxia; Neurons; Quinoxalines; Rats; Rats, Wistar; Receptors, AMPA; Receptors, Kainic Acid; Receptors, N-Methyl-D-Aspartate; Sodium; Sodium Channel Blockers; Sodium Channels; Sodium-Calcium Exchanger; Tetrodotoxin; Thiourea

The effect of N-methyl-D-aspartate (NMDA) and 2-(aminomethyl)phenylacetic acid/kainate (AMPA/kainate) glutamate receptors on dentate cell proliferation and hippocampal synapsin-I induction was examined after global ischemia. Cell proliferation was assessed using BrdU labeling, and synaptic responses were assessed using synapsin-I expression. Systemic glutamate receptor antagonists (MK-801 and NBQX) increased BrdU-labeled cells in the dentate subgranular zone (SGZ) of control adult gerbils (30% to 90%, P < 0.05). After global ischemia (at 15 days after 10 minutes of ischemia), most CA1 pyramidal neurons died, whereas the numbers of BrdU-labeled cells in the SGZ increased dramatically (>1000%, P < 0.0001). Systemic injections of MK801 or NBQX, as well as intrahippocampal injections of either drug, when given at the time of ischemia completely blocked the birth of cells in the SGZ and the death of CA1 pyramidal neurons at 15 days after ischemia. Glutamate receptor antagonists had little effect on cell birth and death when administered 7 days after ischemia. The induction of synapsin-I protein in stratum moleculare of CA3 at 7 and 15 days after global ischemia was blocked by pretreatment with systemic or intrahippocampal MK-801 or NBQX. It is proposed that decreased dentate glutamate receptor activation--produced by glutamate receptor antagonists in normal animals and by chronic ischemic hippocampal injury--may trigger dentate neurogenesis and synaptogenesis. The synapsin-I induction in mossy fiber terminals most likely represents re-modeling of dentate granule cell neuron presynaptic elements in CA3 in response to the ischemia. The dentate neurogenesis and synaptogenesis that occur after ischemia may contribute to memory recovery after hippocampal injury caused by global ischemia.

Topics: Animals; Brain Ischemia; Cell Division; Dentate Gyrus; Dizocilpine Maleate; Down-Regulation; Excitatory Amino Acid Antagonists; Gerbillinae; Glutamic Acid; Male; Memory; Microinjections; Neurons; Neuroprotective Agents; Quinoxalines; Receptors, AMPA; Receptors, Glutamate; Receptors, Kainic Acid; Receptors, N-Methyl-D-Aspartate; Synapsins

Transient forebrain ischemia results in a 24- to 72-hour delayed loss of CA1 neurons. Previous work has not assessed whether insult durations can vary the degree and maturation rate of CA1 injury and whether there are different ultrastructural features of death after brief or severe ischemia. We also tested whether known cytoprotective drugs achieve permanent or transient neuroprotection.. In the first experiment, ischemia was induced for 5, 15, or 30 minutes with the use of the 4-vessel occlusion rat model with 1- to 28-day survival. Others subjected to 5 or 15 minutes of ischemia and allowed to survive for 14 or 7 days, respectively, were examined with electron microscopy. Finally, we determined whether NBQX (30 mg/kg x3 at 0 or 6 hours after ischemia), an AMPA antagonist, and SNX-111 (5 mg/kg at 6 hours after ischemia), an N-type Ca2+ channel antagonist, provided enduring CA1 protection against 10 minutes of ischemia.. CA1 damage was not detected at 24 hours. Thirty minutes of ischemia produced 47% and 84% CA1 damage at 2 and 3 days, respectively. A 15-minute occlusion yielded 11%, 74%, and 86% loss at 2, 3, and 7 days, respectively. Five minutes of ischemia produced an even slower progression with 24%, 52%, and 59% loss at 3, 7, and 14 days, respectively. Ultrastructural examination after 5 and 15 minutes of ischemia revealed necrosis with no morphological evidence of apoptosis. Both NBQX (P<0.021) and SNX-111 (P<0.001) significantly reduced CA1 death at 7 days (/=80%) compared with saline treatment ( approximately 79%).. Brief forebrain ischemia results in a slower progression of CA1 loss than more severe insults. Nonetheless, neuronal injury had necrotic, not apoptotic, morphology. NBQX and SNX-111 only postponed CA1 injury.

Topics: Animals; Brain Ischemia; Cell Death; Hippocampus; Male; Neurons; Neuroprotective Agents; omega-Conotoxins; Peptides; Quinoxalines; Rats; Rats, Wistar; Time Factors

Cyclooxygenase-2 (COX-2) is implicated in ischemic neuronal death. In focal ischemia, its mRNA induction is mediated through N-methyl-D-aspartic acid (NMDA) receptors and phospholipase A(2). Because mechanisms of neuronal death involving COX-2 in global ischemia are unclear, we studied the time course and regulation of COX-2 expression in rat brain global ischemia.. Global ischemia was induced by a 4-vessel occlusion method. COX-2 mRNA levels were demonstrated with in situ hybridization and COX-2 protein with immunocytochemistry. Several animals were pretreated with MK-801, an NMDA receptor antagonist; 2, 3-dihydroxy-6-nitro-7-sulfamoyl-benzo(F)quinoxaline (NBQX), an alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor antagonist; and dexamethasone.. In the cortex, the CA3 hippocampal region and dentate gyrus expression of COX-2 mRNA peaked at 4 to 8 hours, while in the CA1 region COX-2 mRNA levels were high at 4 to 24 hours. COX-2 protein was induced in the corresponding regions at 12 to 24 hours, but in the CA1 neurons the protein was still seen at 3 days. COX-2 mRNA induction in the cortex was inhibited by NBQX and dexamethasone and in CA1 neurons was inhibited by NBQX. MK-801 did not suppress COX-2 induction.. COX-2 is differentially induced in the cortex and hippocampal structures after global ischemia. The prolonged COX-2 expression in the vulnerable CA1 neurons is regulated by AMPA receptors, suggesting that COX-2 expression is likely to be associated with AMPA receptor-mediated neuronal death in global ischemia. Glucocorticoids may not be efficiently used to inhibit ischemia-induced COX-2 expression in the hippocampus.

Topics: Animals; Brain Ischemia; Cerebral Cortex; Cyclooxygenase 2; Dexamethasone; Excitatory Amino Acid Antagonists; Glucocorticoids; Isoenzymes; Male; Prostaglandin-Endoperoxide Synthases; Quinoxalines; Rats; Rats, Wistar; Receptors, AMPA; RNA, Messenger; Time Factors; Tissue Distribution

Spreading depression is a wave of sustained depolarization challenging the energy metabolism of the cells without causing irreversible damage. In the ischaemic brain, sreading depression-like depolarization contributes to the evolution of ischaemia to infarction. The depolarization is propagated by activation of N-methyl-D-aspartate receptors, but changes in signal transduction downstream of the receptors are not known. Because protein phosphorylation is a general mechanism whereby most cellular processes are regulated, and inhibition of N-methyl-D-aspartate receptors or protein kinase C is neuroprotective, the expression of protein kinase C subspecies in spreading depression was examined. Cortical treatment with KCl induced an upregulation of protein kinase Cdelta and zeta messenger RNA at 4 and 8 h, whereas protein kinase Calpha, beta, gamma and epsilon did not show significant changes. The gene induction was the strongest in layers 2 and 3, and was followed by an increased number of protein kinase Cdelta-immunoreactive neurons. Protein kinase Cdelta and zeta inductions were inhibited by pretreatment with an N-methyl-D-aspartate receptor antagonist, dizocilpine maleate, which also blocked spreading depression propagation, and with dexamethasone, which acted without blocking the propagation. Quinacrine, a phospholipase A2 inhibitor, reduced only protein kinase C5 induction. In addition, N(G)(-nitro-L-arginine methyl ester, a nitric oxide synthase inhibitor, did not influence protein kinase Cdelta or zeta induction, whereas 6-nitro-7-sulphamoylbenzo[f]quinoxaline-2,3-dione, an alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate/kainate receptor antagonist, and the cyclo-oxygenase inhibitors indomethacin and diclophenac tended to increase gene expression. The data show that cortical spreading depression induces Ca2(+)-independent protein kinase C subspecies delta and zeta, but not Ca(2+)-dependent subspecies, through activation of N-methyl-D-aspartate receptors and phospholipase A2. Even though the signal pathway is similar to the induction described previously in ischaemia for genes implicated in delayed neuronal death, the gene inductions observed here are not necessarily pathogenetic, but may represent a general reaction to metabolic stress.

Topics: alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; Animals; Brain Ischemia; Cortical Spreading Depression; Cyclooxygenase Inhibitors; Dexamethasone; Diclofenac; Disease Susceptibility; Dizocilpine Maleate; Enzyme Induction; Enzyme Inhibitors; Excitatory Amino Acid Antagonists; Gene Expression Regulation, Enzymologic; Indomethacin; Isoenzymes; Male; Nerve Tissue Proteins; NG-Nitroarginine Methyl Ester; Nitric Oxide Synthase; Parietal Lobe; Phospholipases A; Phospholipases A2; Promoter Regions, Genetic; Protein Kinase C; Protein Kinase C-delta; Quinacrine; Quinoxalines; Rats; Rats, Wistar; Receptors, Kainic Acid; Receptors, N-Methyl-D-Aspartate; Signal Transduction; Transcriptional Activation

The diazoxide derivative IDRA 21 and other positive modulators of (AMPA)-type glutamate receptors are considered potential memory-enhancing agents. However, AMPA receptor activation contributes to CA1 hippocampal neuron damage from global ischemia in rodents, raising the possibility that 7-chloro-3-methyl-3-4-dihydro-2H-1,2,4 benzothiadiazine S,S-dioxide (IDRA 21) or drugs with similar actions may worsen ischemic neuronal injury. Here we demonstrate that glutamate plus IDRA 21 kills cultured rat hippocampal neurons by AMPA receptor activation, and, in vivo, 12 and 24 mg/kg of IDRA 21 given orally increases CA1 neuron loss produced by 10 minutes of global ischemia. Treating patients with drugs that potentiate AMPA receptor activation will have to consider these potential effects, particularly when coexistent with conditions in which excessive activation of AMPA receptors may occur (eg, stroke, seizures).

Topics: Animals; Benzothiadiazines; Brain Ischemia; Cells, Cultured; Diazoxide; Diuretics; Excitatory Amino Acid Antagonists; Glutamic Acid; Hippocampus; Nerve Degeneration; Neurons; Neurotoxins; Quinoxalines; Rats; Rats, Inbred Strains; Receptors, AMPA; Sodium Chloride Symporter Inhibitors

Deep prepiriform cortex modulates excitatory activity in the limbic system during seizures. We therefore studied a potential role for this system in another process involving excitatory neurotransmission: global ischemia in the rat. The non-NMDA antagonist NBQX was microinjected bilaterally into deep prepiriform cortex prior to 10 min of global ischemia. Hippocampal cell injury was then assessed by heath shock protein (HSP) expression 24 h after ischemia. NBQX significantly decreased the number of HSP positive cells in both CA1 and CA3 hippocampal subsectors, suggesting the possibility that pathways from deep prepiriform cortex to hippocampus modulate excitotoxicity in target neurons during ischemia.

Topics: Animals; Biomarkers; Brain Ischemia; Cerebral Cortex; Excitatory Amino Acid Antagonists; Heat-Shock Proteins; Hippocampus; HSP72 Heat-Shock Proteins; Immunohistochemistry; Male; Neurons; Quinoxalines; Rats; Rats, Sprague-Dawley; Receptors, N-Methyl-D-Aspartate

The alpha-amino-3-hydroxy-5-methyl-4-isoxazole (AMPA) receptor antagonist, 2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo(F)quinoxaline (NBQX), offers protection to hippocampal CA1 pyramidal cells after short episodes of transient cerebral ischemia. Besides CA1 pyramidal cells, neurons containing somatostatin (SS) and located in the dentate hilus of the hippocampal formation are lost after cerebral ischemia. We studied the protective effects of NBQX on SS neurons in the hilus and on hippocampal CA1 pyramidal cells following 8, 10, or 12 min of four-vessel occlusion ischemia during systemic hypotension. NBQX was administered 3 x 30 mg/kg at 0, 10, and 25 after induction of ischemia or sham, and all rats survived for 7 days. NBQX given to control rats without ischemia had no influence on number or morphology of hilar SS neurons and CA1 pyramidal cells. After 8 min of ischemia, NBQX prevented loss of hilar SS neurons. After 10 and 12 min of ischemia, NBQX had no significant effects on loss of SS neurons in the dentate hilus. However, in all ischemic groups, NBQX significantly reduced loss of CA1 pyramidal cells as compared to control rats. This neuroprotective effect decreased gradually and significantly as the time of ischemia increased. Our results support the observation that SS neurons in hilus are among the most ischemia-vulnerable neurons in the brain. We found that administration of NBQX in generally accepted dosages can protect the rapidly dying SS neurons in hilus from only brief episodes of ischemia.

Topics: Animals; Brain Ischemia; Cell Death; Dentate Gyrus; Excitatory Amino Acid Antagonists; Hippocampus; Ligation; Male; Nerve Tissue Proteins; Neurons; Neuroprotective Agents; Pyramidal Cells; Quinoxalines; Rats; Rats, Wistar; Receptors, AMPA; Shock; Somatostatin; Time Factors

We have previously shown that treatment with glutamate receptor antagonists after focal ischemia can partially reverse acute lesions measured with diffusion-weighted MRI. The goal of this study was to examine the quantitative nature of these effects of neuroprotection.. Rats were subjected to permanent occlusion of the middle cerebral artery under halothane anesthesia and treated with 2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo(F)quinoxaline (NBQX) (30 mg/kg IP; two doses given immediately after ischemia and 1 hour after ischemia) or given injections of saline. Diffusion-weighted MRI scans were performed to map the changes in water diffusivity during the first 3 hours after ischemia. Apparent diffusion coefficients (ADCs) within the ischemic hemisphere were calculated, and ischemic changes were expressed as absolute reductions and as a percentage of contralateral mean values. Relative perfusion deficits in the ischemic hemisphere were assessed with dynamic MRI of transient changes in transverse relaxation rates (delta R2*).. Analysis with ADC probability distribution functions showed that focal ischemia was present with gradients in ADC reductions emanating from the center to the periphery of the lesion. Ischemic evolution in control rats was manifested as a progressive shift of the probability distribution functions over time. NBQX treatment resulted in a reverse shift of these probability functions. By 3 hours after occlusion, probability distribution functions were significantly improved in treated rats (P < .05). Because of the temporal evolution of the probability distribution functions, ADC thresholds that correlated with histological outcomes of infarction changed over time. NBQX did not alter the cerebral perfusion index, measured as delta R2* peak values.. The results indicate that ADC probability distribution functions can be used to quantitatively evaluate the effects of neuroprotective treatment on the gradients of injury in focal cerebral ischemia. The probability functions also allow for intrasubject comparisons and may therefore be useful for exploring therapeutic windows.

Topics: Animals; Body Water; Brain Damage, Chronic; Brain Edema; Brain Ischemia; Cerebral Infarction; Diffusion; Excitatory Amino Acid Antagonists; Magnetic Resonance Imaging; Male; Nerve Tissue Proteins; Neuroprotective Agents; Quinoxalines; Rats; Rats, Sprague-Dawley; Receptors, AMPA

Deep prepiriform cortex has an important role in modulating neurotransmission during limbic seizures. We used pharmacologic blockade of non-N-methyl-D-aspartate (NMDA) receptors to study excitatory circuitry from the deep prepiriform cortex to the hippocampus during global ischemia in rat. NBQX, a potent non-NMDA glutamate receptor antagonist, was microinjected stereotactically into the deep prepiriform cortex before global ischemia for 10 min. Neuronal cell death in the hippocampus was evaluated quantitatively 72 h after ischemia. The NBQX-injected rats had a greater number of surviving cells in CA1 sector of hippocampus than did saline-injected controls or rats that received NBQX injections 1 mm from the target. Thus, excitatory amino acid-mediated circuitry emanating from deep prepiriform cortex modulates ischemic neuronal injury in the hippocampus.

Topics: Animals; Brain Ischemia; Cell Count; Cell Death; Excitatory Amino Acid Antagonists; Hippocampus; Male; Microinjections; Neurons; Neuroprotective Agents; Olfactory Pathways; Premedication; Quinoxalines; Rats; Rats, Sprague-Dawley; Receptors, N-Methyl-D-Aspartate; Seizures; Stereotaxic Techniques

Glial inclusions containing the microtubule-associated protein tau are present in a variety of chronic neurodegenerative conditions. We now report a rapid and time-dependent increase of tau immunoreactivity within oligodendrocytes after focal cerebral ischemia in the rat. The number of tau positive oligodendrocytes in the ipsilateral subcortical white matter increased six- to eightfold by 40 minutes after permanent middle cerebral artery occlusion (MCAO). Tau was detected using antibodies that label both the N- and C-terminal of the protein, suggesting accumulation of full-length protein within these cells. Pretreatment with the spin trap agent alpha-phenyl-tert-butyl-nitrone (PBN)(100mg/kg) reduced the number of tau-positive oligodendrocytes by 55% in the subcortical white matter of the ischemic hemisphere compared with untreated animals at 40 minutes after MCAO. In contrast, pretreatment with glutamate receptor antagonists MK-801 (0.5 mg/kg) or 2,3-dihydroxy-6-nitro-7-sulpfamoyl-benzo(f)quinoxaline (NBQX) (2 x 30 mg/kg), failed to reduce the number of tau-positive oligodendrocytes after 40 minutes of ischemia. The results indicate that oligodendrocytes respond rapidly to an ischemic challenge and that free radical-mediated mechanisms are involved in the cascade leading to increased tau immunoreactivity.

Topics: Animals; Brain Ischemia; Caudate Nucleus; Cerebral Cortex; Cyclic N-Oxides; Dizocilpine Maleate; Excitatory Amino Acid Antagonists; Free Radicals; Immunohistochemistry; Male; Microtubule-Associated Proteins; Nitrogen Oxides; Oligodendroglia; Quinoxalines; Rats; Rats, Inbred F344; Spin Labels; tau Proteins

We investigated the neuroprotective effect of the alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA)-receptor antagonist YM90K in transient global ischemia models. In a gerbil model, transient ischemia was induced by bilateral common carotid artery (CCA) occlusion for 5 min. On administration at 1 hr after ischemia, the AMPA antagonists NBQX (30 mg/kg, i.p. x 3) and YM90K (15 mg/kg, i.p. x 3 or 30 mg/kg, i.p. x 3) significantly reduced the delayed neuronal death in the hippocampal CA1 region from 4 days after bilateral CCA occlusion. Furthermore, YM90K (30 mg/kg, i.p. x 3) showed a neuroprotective effect even when given at 6 hr after ischemia. In contrast, the N-methyl-D-aspartate receptor antagonists CGS19755, MNQX (30 mg/kg, i.p. x 3, each) and (+/-)MK-801 (10 mg/kg, i.p.) were not effective on injection at 1 hr after ischemia in this model. In a rat model, ischemia was induced by 4-vessel occlusion (4-VO) for 10 min. YM90K was administered 60 min after reperfusion. Rectal and temporal muscle temperatures were maintained at the same level as in the control group for 6 hr. YM90K markedly prevented the development of delayed neuronal death from 7 days after 4-VO at doses of 15 or 30 mg/kg, i.p. x 3, with neuroprotective efficacy similar to that in the gerbil model. These results suggest that the AMPA receptor plays a critical role in the development of the delayed neuronal death induced by transient global cerebral ischemia. They also suggest that the neuroprotective effect of YM90K is not related to its hypothermic effect.

Topics: Animals; Body Temperature; Brain Ischemia; Cell Death; Dose-Response Relationship, Drug; Excitatory Amino Acid Antagonists; Gerbillinae; Hippocampus; Male; Neurons; Neuroprotective Agents; Quinoxalines; Rats; Rats, Wistar

Topics: Acoustic Stimulation; alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; Animals; Anticonvulsants; Brain Injuries; Brain Ischemia; Cerebral Cortex; Convulsants; Excitatory Amino Acid Antagonists; Exploratory Behavior; Kindling, Neurologic; Male; Mice; Mice, Inbred Strains; Neuroprotective Agents; Quinoxalines; Rats; Rats, Inbred F344; Rats, Sprague-Dawley; Rats, Wistar; Seizures

Recently, we reported the synthesis of 3-(sulfonylamino)-2(1H)-quinolones, a new series of alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA)/kainate and N-methyl-D-aspartic acid (NMDA)/glycine antagonists. By exploring the structure-activity relationships (SAR) in this series, we were able to identify the 6,7-dinitro derivative 6 as a potent and balanced antagonist at both receptors. Unfortunately, compound 6 was devoid of in vivo activity in mice anticonvulsant testing. To overcome this critical limitation, new compounds bearing various acidic moieties at the 3-position of the quinolone skeleton were synthesized and evaluated. The SAR of these new analogues indicated that not all acidic groups are acceptable at the 3-position: A rank order of potency going from carboxylic approximately phosphonic > tetrazole > mercaptoacetic > hydroxamic >> other heterocyclic acids was defined. In addition, the selectivity between the AMPA/kainate and NMDA/glycine sites is dependent on the nature of the substitution (nitro > chloro for AMPA selectivity), its position (5,7- > 6,7-pattern for glycine selectivity), and the distance between the quinolone moiety and the heteroatom bearing the acidic hydrogen (the longer the distance the more AMPA selective the compound). Among these new AMPA antagonists, we have identified 6,7-dichloro-2(1H)-oxoquinoline-3-phosphonic acid (24c) as a water soluble and selective compound endowed with an appealing pharmacological profile. Compared with the reference AMPA antagonist NBQX, the phosphonic acid 24c is much less potent in vitro but almost equipotent in vivo in the audiogenic seizures model after intraperitoneal administration. Moreover, unlike NBQX, compound 24c is also active after oral administration. In the gerbil global ischemia model, compound 24c shows a neuroprotective effect at 10 mg/kg/ip, equivalent to the reference NBQX.

Topics: alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; Animals; Brain; Brain Ischemia; Electrophysiology; Excitatory Amino Acid Agonists; Excitatory Amino Acid Antagonists; Gerbillinae; Kainic Acid; Mice; Molecular Structure; N-Methylaspartate; Neuroprotective Agents; Organophosphonates; Quinolones; Quinoxalines; Rats; Receptors, AMPA; Receptors, N-Methyl-D-Aspartate; Structure-Activity Relationship; Xenopus

AMPA antagonists have been shown to be remarkably neuroprotective in models of global ischemia, but the data in focal ischemia remain controversial. We, therefore, studied the dose-response characteristics and the time window of efficacy of the AMPA antagonist NBQX in a rat model of permanent focal ischemia. NBQX 40, 60 or 100 mg/kg i.v., substantially reduced infarct size. Neuroprotection was maintained when the initiation of drug administration was withheld for 15, 45 or 90 min after permanent middle cerebral artery occlusion. Furthermore, NBQX did not induce heat shock protein in cingulate cortex, as do some N-methyl-D-aspartate antagonists. Thus, the compound is a potent neuroprotectant in focal ischemia and has an unusually long time window of effectiveness.

Topics: Animals; Brain; Brain Ischemia; Cerebral Arteries; Cerebral Infarction; Dizocilpine Maleate; Dose-Response Relationship, Drug; Excitatory Amino Acid Antagonists; Heat-Shock Proteins; Male; N-Methylaspartate; Quinoxalines; Rats; Rats, Sprague-Dawley; Receptors, AMPA

Stroke trials are initiated after demonstrated pharmacological protection in animal models. NBQX protects CA1 neurons against global ischemia; however, this glutamate antagonist induces a period of subnormal temperature (e.g., a decrease of only 1.0-1.5 degrees C) lasting several days. In this study, NBQX (3 x 30 mg/kg, i.p.) was administered starting 60 min after reperfusion, and brain temperature had declined significantly below vehicle-treated animals by 2 h after reperfusion. When the postischemic brain temperature of NBQX-treated gerbils was regulated, no neuronal protection was found. Mimicking an NBQX-induced temperature profile for 28 h postischemia yielded histological protection 4 days later comparable to that of NBQX. However, both the NBQX and temperature simulation groups showed decreased protection after 10-day survival. Our data suggest that a protracted period of subnormal temperature during postischemic period can obscure the interpretation of preclinical drug studies.

Topics: alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; Animals; Body Temperature; Brain; Brain Ischemia; Gerbillinae; Hypothermia, Induced; Neuroprotective Agents; Quinoxalines; Rats; Rats, Sprague-Dawley; Reperfusion; Time Factors

Glutamate receptors are numerous on the ischemia vulnerable CA-1 pyramidal cells. Postischemic use of the AMPA antagonist NBQX has shown up to 80% protection against cell death. Three aspects of this were studied: In the first study, male Wistar rats were given NBQX (30 mg/kg x 3) either 20 hours or immediately (0 h) before 12 min of 4-vessel occlusion with hypotension. After six days of reperfusion comparison with an untreated group showed almost full protection in the 0 h group (4% cell loss, p < 0.001) but only slight protection in the 20 h group (62% cell loss, p < 0.05). After 12 min of ischemia in the present model, eosinophilic CA-1 cells are seen from day 2 on. Since there could be a late, deleterious calcium influx via NMDA receptors, one group of ischemic rats was given MK-801 (5 mg/kg i.p.) 24 hours after ischemia. However, quantitation 6 days later of remaining CA-1 cells showed no protection. In the third study referred here, two groups of ischemic rats were given NBQX (30 mg/kg x 3) immediately after ischemia. The groups survive for six and 21 days, respectively. Counting of CA-1 pyramidal cells showed an equal, significant protection in both groups (approx 20% cell loss).

Topics: Animals; Brain Damage, Chronic; Brain Ischemia; Brain Mapping; Dizocilpine Maleate; Dose-Response Relationship, Drug; Drug Administration Schedule; Excitatory Amino Acid Antagonists; Glutamic Acid; Hippocampus; Male; Neurons; Premedication; Quinoxalines; Rats; Rats, Wistar; Receptors, AMPA; Receptors, N-Methyl-D-Aspartate

Topics: Animals; Brain Ischemia; Excitatory Amino Acid Antagonists; Microdialysis; Neurotoxins; Quinoxalines

To evaluate the role played by nitric oxide in global cerebral ischaemia we examined the effects of 7-nitroindazole and a sodium salt of 7-nitroindazole (inhibitors of neuronal nitric oxide (NO) synthase) and NG-nitro-L-arginine methyl ester (a more general inhibitor of NO synthase) in the gerbil model of cerebral ischaemia. Four experiments were carried out. In the first experiment, animals were either sham-operated, subjected to 5 min bilateral carotid occlusion (BCAO) or administered 7-nitroindazole or NG-nitro-L-arginine methyl ester immediately after occlusion followed by three further doses at 3, 6 and 24 h post-occlusion. In the second experiment, we examined the effects of a sodium salt of 7-nitroindazole, which is more soluble than 7-nitroindazole, using the same protocol. In the third experiment, the effects of the sodium salt of 7-nitroindazole administered at 10 mg/kg at 0, 3, 6, 24, 27, 30, 33, 52, 55, 72, 75 and 78 h post-occlusion or at 0.05 mg/h for 72 h via mini-pumps were evaluated. In separate experiments, we examined the effects of three reference compounds dizocilpine (MK-801), 2, 3-dihydroxy-6-nitro-7-sulphamoyl-benz(F)-quinoxaline (NBQX) and eliprodil using the same model. Extensive neuronal death was observed in the CA1 layer of the hippocampus in 5 min bilateral carotid occluded animals 5 days after surgery. Both 7-nitroindazole and NG-nitro-L-arginine methyl ester provided significant neuroprotection (P < 0.01) against this neuronal death. The sodium salt of 7-nitroindazole showed no protection when administered up to 12 times post-occlusion, but did provide significant (P < 0.01) neuroprotection when administered via mini-pump. The neuroprotection was similar to that provided by MK-801 and eliprodil, but not as good as that observed with NBQX. These results indicate that nitric oxide plays a role in ischaemic cell death and that selective neuronal nitric oxide synthase inhibitors can protect against ischaemic brain damage.

Topics: Animals; Brain Ischemia; Disease Models, Animal; Dizocilpine Maleate; Enzyme Inhibitors; Gerbillinae; Indazoles; Male; Neuroprotective Agents; NG-Nitroarginine Methyl Ester; Nitric Oxide Synthase; Piperidines; Quinoxalines

We investigated the temporo-spatial expression of astrocyte glial fibrillary acidic protein (gfap) and sulfated glycoprotein 2 (sgp-2) mRNAs in comparison to 70-kDa heat shock protein (hsp70) mRNA by in situ hybridisation in rats subjected to permanent occlusion of the middle cerebral artery (MCA). Gfap mRNA started to increase in the cingulate cortex of the lesioned hemisphere 6 h after MCA occlusion and gradually spread over the lateral part of the ipsilateral cortex and the striatum from 12 h to 3 days, peaking at 3 days after MCA occlusion. Gfap mRNA also increased in the contralateral cingulate cortex and corpus callosum at 12 and 24 h. Hsp70 mRNA increased markedly in the ipsilateral cortex adjacent to the ischemic lesion, and slightly within the lesion area from 3 to 24 h and disappeared after 3 days. By 7 days, gfap and sgp-2 mRNAs were increased markedly in the peri-infarct area, and in the ipsilateral thalamus parallel with the delayed neuronal damage, whereas the widespread increase of gfap mRNA in the ipsilateral hemisphere declined. Post-occlusion treatment with the glutamate receptor antagonists MK-801 and NBQX slightly attenuate the induction of gfap but did not qualitatively affect the topical expression pattern. Within the cingulate cortex MK-801 treatment resulted in a significant decrease of the signal intensity at all survival times, reflecting most likely an attenuation of lesion-induced spreading depression like depolarization waves by MK-801. The area of hsp70 expression was reduced by both MK-801 and NBQX, most likely reflecting the decrease of the lesion area by both treatment regimens. Our study thus revealed an early and widespread increase of gfap mRNA in the non-ischemic area including the contralateral hemisphere starting between 3 and 6 h, and a delayed circumscribed expression in the peri-infarct border zone after 1 week. Comparison with the expression of hsp70 mRNA suggests that the absence of an early gfap mRNA induction in the peri-lesion zone reflects an impairment of astrocytic function which may be of importance for infarct growth during the early evolution of the pathological process.

Topics: Animals; Astrocytes; Brain Ischemia; Clusterin; Dizocilpine Maleate; Electroencephalography; Excitatory Amino Acid Antagonists; Glial Fibrillary Acidic Protein; Glycoproteins; HSP70 Heat-Shock Proteins; In Situ Hybridization; Male; Molecular Chaperones; Quinoxalines; Rats; Rats, Inbred F344; RNA, Messenger; Time Factors

Brain microdialysis was used to study changes in the glutamate and aspartate extracellular concentrations in the striatum of conscious rats submitted to 30 minutes cerebral ischaemia, using the four-vessel occlusion model. Perfusion of the N-methyl-D-aspartate (NMDA) receptor channel blockers, dizocilpine (MK-801; 75 microM) and Mg2+ (2.5 mM), inhibited the ischaemia-induced accumulation of glutamate and aspartate. The AMPA/kainate receptor antagonist, 2,3-dihydroxy-6-nitro-7-sulfamylbenzo (F) quinoxaline (NBQX; 15 microM and 450 microM) had no effect on glutamate and aspartate levels during ischaemia. On the other hand, omission of Ca2+ from the perfusing solution did not alter the increases in glutamate and aspartate induced by ischaemia. These results suggest that the glutamate and aspartate accumulation in four-vessel occlusion ischaemia is mediated by activation of NMDA receptors in a Ca2+ independent manner.

Topics: Animals; Aspartic Acid; Brain Ischemia; Calcium; Corpus Striatum; Dizocilpine Maleate; Glutamic Acid; Magnesium; Male; Microdialysis; Prosencephalon; Quinoxalines; Rats; Rats, Wistar; Receptors, AMPA; Receptors, N-Methyl-D-Aspartate

A large body of evidence exists to demonstrate that excitatory amino acids (EAA) and their receptors are involved in the pathophysiological mechanisms linking several acute brain insults, such as cerebral ischemia, to neuronal degeneration and death. Accordingly, the use of EAA receptor antagonists can be beneficial in attenuating or preventing the neuronal irreversible damage subsequent to various neuropathological syndromes. We have investigated the effect of 15 min of simulated ischemic conditions, i.e., oxygen/glucose deprivation, on hippocampal slices preparation measuring, as neurotoxicity indexes, both the amino acids efflux in the incubation medium, detected by HPLC, and the inhibition of protein synthesis, evaluated as 3H-Leucine incorporation into proteins. Accumulation of neurotransmitter amino acids was measured in the medium during the "ischemic" period. Glutamate increased 30-fold over the basal level while aspartate was sevenfold and GABA 12-fold higher than in normal conditions. After a reoxygenation period of 30 min, the rate of protein synthesis of hippocampal slices subjected to "ischemia" was reduced to 35-50% of controls. The non-competitive NMDA antagonist MK-801 (100 microM) and the competitive NMDA antagonist CGP 39551 (100-250 microM) as well as the non-NMDA receptor antagonists NBQX (100 microM) and AP3 (300 microM) were unable to counteract the metabolic impairment when they were present alone in the incubation fluid during simulated "ischemia." An incomplete, but highly significant (p < 0.001), protection from protein synthesis impairment was achieved in the presence of an equimolar concentration (100 microM) of MK-801 and NBQX.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: 2-Amino-5-phosphonovalerate; Amino Acids; Animals; Brain Ischemia; Dizocilpine Maleate; Excitatory Amino Acid Antagonists; Glucose; Hippocampus; In Vitro Techniques; Ionophores; Leucine; Male; Nerve Tissue Proteins; Quinoxalines; Rats; Rats, Wistar; Receptors, AMPA; Receptors, N-Methyl-D-Aspartate

This study examines the relationship between the concentration of extracellular glutamate released during 30 min of forebrain ischemia, and the subsequent development of ischemic neural necrosis, in the presence of three agents which act at distinct sites on the glutamatergic synapse: a presynaptic inhibitor of glutamate release (5-(2,3,5-trichlorophenyl)-2,4-diamino-pyramidine ethane sulphonate (BW1003C87)); a competitive NMDA receptor antagonist (cis-4-phosphonomethyl-2-piperidine carboxylic acid (CGS19755)); and a competitive AMPA receptor antagonist (2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo(F)quinoxaline (NBQX)). Pretreatment with either BW1003C87 or NBQX markedly attenuated the peak concentration of extracellular glutamate and offered protection from post-ischemic neuronal necrosis in the CA1 hippocampus. In contrast, pretreatment with CGS19755 had no effect on extracellular glutamate release and did not protect CA1 hippocampal neurons from ischemic injury.

Topics: Analysis of Variance; Animals; Binding, Competitive; Brain Ischemia; Disease Models, Animal; Glutamic Acid; Hippocampus; Injections, Intraperitoneal; Injections, Intravenous; Male; Microdialysis; N-Methylaspartate; Necrosis; Neurons; Observer Variation; Pipecolic Acids; Prosencephalon; Pyrimidines; Quinoxalines; Random Allocation; Rats; Rats, Wistar; Receptors, AMPA; Reperfusion Injury

In a model of perinatal hypoxic-ischemic brain damage, we examined the neuroprotective efficacy of posttreatment with the NMDA receptor antagonist MK-801 and the AMPA receptor antagonist NBQX. Unilateral brain damage developed in 95% of rat pups subjected to hypoxia-ischemia with a 27.8 +/- 1.2% weight deficit of the damaged hemisphere. MK-801 in doses of 0.3 and 0.5 mg/kg i.p. reduced the brain damage by 61% (p < 0.001) and 43% (p < 0.001), respectively. A higher dose of MK-801 (0.75 mg/kg) did not offer neuroprotection. Treatment with NBQX (40 mg/kg) reduced the hemispheric lesion by 28% (p < 0.05). In conclusion, posttreatment with both NBQX and low doses of MK-801 reduced perinatal brain damage. The NMDA receptor antagonist offered stronger neuroprotection which is in agreement with a proposed NMDA receptor hyperactivity around postnatal day 7 in rats.

Topics: Animals; Animals, Newborn; Brain Damage, Chronic; Brain Ischemia; Disease Models, Animal; Dizocilpine Maleate; Dose-Response Relationship, Drug; Female; Hypoxia, Brain; Injections, Intraperitoneal; Male; Quinoxalines; Rats; Rats, Wistar; Receptors, AMPA; Severity of Illness Index; Treatment Outcome

The effect of the AMPA antagonist NBQX on peri-infarct inhibition of cerebral protein synthesis (CPS) was studied in rats subjected to 3 h occlusion of the left middle cerebral artery (MCA). Cerebral blood flow and CPS were measured with double tracer autoradiography and local ATP content was monitored by bioluminescence imaging. In untreated MCA-occluded animals the perfusion threshold of ATP depletion in cerebral cortex was 17 +/- 5 ml 100 g-1 min-1 and that of CPS inhibition was 49 +/- 13 ml 100 g-1 min-1. NBQX treatment (2 x 30 mg kg-1 after vascular occlusion) reduced the perfusion threshold of CPS inhibition to 16 +/- 6 ml 100 g-1 min-1 (p < 0.05) whereas that of ATP depletion was not affected (11 +/- 6 ml 100 g-1 min-1). The NBQX-induced pharmacological improvement of peri-infarct CPS is similar to the previously described amelioration of peri-infarct CPS by MK-801 and may contribute to the reduction of infarct size by this treatment.

Topics: Adenosine Triphosphate; Animals; Brain; Brain Ischemia; Differential Threshold; Male; Nerve Tissue Proteins; Quinoxalines; Rats; Rats, Inbred Strains; Receptors, AMPA

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

2,3-Dihydroxy-6-nitro-7-sulfamoylbenzo(F)-quinoxaline (NBQX), an alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptor antagonist, has been reported to provide neuronal protection after global ischemia. The objectives of this study were to evaluate the neuroprotective effects of NBQX initiated after focal cortical ischemia and to validate a method for measuring functional outcome in this model. Male spontaneously hypertensive rats (SHRs) were exposed to various durations of transient or permanent tandem middle cerebral artery (MCA) occlusion. Studies compared motor performance using balance beam and prehensile-traction tests, calcium-calmodulin (Ca-CaM) binding by immunohistochemistry, and infarct volume between NBQX-treated animals [intravenous (i.v.) 5 mg/kg/h x 6 h or intraperitoneal (i.p.) 30 mg/kg q 30 min x 3 begun postischemia] and controls. All ischemic groups performed less well than sham-operated controls on the motor performance tasks in proportion to the severity of ischemia. No significant improvement in motor performance was noted in the NBQX-treated versus the control animals after 1 h or permanent MCA/CCA occlusion. Treatment with NBQX (i.v. or i.p. dosing) did not reduce Ca-CaM binding after 1 h of occlusion with 1 h of reperfusion or after 2 h of occlusion. Similarly, there was no reduction in infarct size between NBQX-treated and control animals after 24 h of permanent MCA/CCA occlusion (74.6 +/- 7.1 vs. 80.1 +/- 6.0 ml; ns) or after 1 h of occlusion with 23 h of reperfusion (55.1 +/- 4.4 vs. 47.4 +/- 6.2 ml; ns).(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Brain; Brain Ischemia; Calcium; Calmodulin; Injections, Intraperitoneal; Injections, Intravenous; Male; Motor Activity; Quinoxalines; Rats; Rats, Inbred SHR

Transient forebrain or global ischemia in rats induces selective and delayed damage of hippocampal CA1 neurons. In a previous study, we have shown that expression of GluR2, the kainate/alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor subunit that governs Ca2+ permeability, is preferentially reduced in CA1 at a time point preceding neuronal degeneration. Postischemic administration of the selective AMPA receptor antagonist, 2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo(f)quinoxaline (NBQX), protects CA1 neurons against delayed death. In this study we examined the effects of NBQX (at a neuroprotective dose) and of MK-801 (a selective NMDA receptor antagonist, not protective in this model) on kainate/AMPA receptor gene expression changes after global ischemia. We also examined the effects of transient forebrain ischemia on expression of the NMDA receptor subunit NMDAR1. In ischemic rats treated with saline, GluR2 and GluR3 mRNAs were markedly reduced in CA1 but were unchanged in CA3 or dentate gyrus. GluR1 and NMDAR1 mRNAs were not significantly changed in any region examined. Administration of NBQX or MK-801 did not alter the ischemia-induced changes in kainate/AMPA receptor gene expression. These findings suggest that NBQX affords neuroprotection by a direct blockade of kainate/AMPA receptors, rather than by a modification of GluR2 expression changes.

Topics: Animals; Autoradiography; Brain; Brain Ischemia; Gene Expression; In Situ Hybridization; Male; Quinoxalines; Rats; Rats, Wistar; Receptors, AMPA; Receptors, Kainic Acid; Receptors, N-Methyl-D-Aspartate; Reperfusion

The ability of five agents (dizocilpine [MK-801], 2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo(F)-quinoxaline [NBQX], enadoline [CI-977], L-nitroarginine methyl ester [L-NAME] and BW 1003c87) with well defined, distinct pharmacological profiles and with established anti-ischemic efficacy, to modify neuronal damage has been examined in a simple in vivo model of glutamate excitotoxicity. Cortical lesions were produced in physiologically-monitored halothane-anesthetised rats by reverse dialysis of glutamate. The volume of the lesion was quantified histologically by image analysis of approximately 20 sections taken at 200 microm intervals throughout the lesion. The AMPA and NMDA receptor antagonists (NBQX and MK-801) and the inhibitor of nitric oxide synthase (L-NAME) significantly reduced the lesion volume by a similar extent (by approximately 30% from vehicle). Two agents (the kappa opioid agonist, CI-977 and the sodium channel blocker, BW 1003c87) which putatively inhibit the release of endogenous glutamate presynaptically, had dissimilar effects on lesion size. CI-977 failed to alter the amount of damage produced by exogenous glutamate, whereas BW 1003c87 reduced the lesion size by approximately 50%. Using this model, the neuroprotective effects of anti-ischemic drugs can be explored in vivo, uncomplicated in contrast to experimental ischemia by reduced oxygen delivery, drug effects on tissue blood flow and compromised energy generation. In consequence, additional mechanistic insight into anti-ischemic drug action in vivo can be obtained.

Topics: Amino Acid Oxidoreductases; Animals; Arginine; Benzofurans; Blood Pressure; Brain Ischemia; Cerebral Cortex; Dizocilpine Maleate; Excitatory Amino Acid Antagonists; Glutamates; Glutamic Acid; Male; Microdialysis; Neurons; Neurotoxins; NG-Nitroarginine Methyl Ester; Nitric Oxide Synthase; Pyrimidines; Pyrrolidines; Quinoxalines; Rats; Rats, Sprague-Dawley; Time Factors

Two glutamate antagonists were tested in a rat model of complete, transient cerebral ischemia. Six days after 10 min ischemia the mean loss of hippocampal CA1 pyramidal neurones was 73%. Administration of the AMPA (alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid) antagonist NBQX (2,3-dihydro-6-nitro-7-sulfamoyl-benzo(F)quinoxaline) reduced the pyramidal neurone loss to 1%, 11% and 15%, when given before, immediately after or 1 h after ischemia, respectively. MK-801 (dizocilpine), a competitive NMDA antagonist gave no protection in this model. We suggest that the AMPA receptor transduction mechanisms are sensitized by ischemia and that the postischemic blockade of the main glutamatergic input to the CA1 cells with NBQX impairs the deleterious effect of "normal" postischemic excitatory transmission.

Topics: Animals; Brain Damage, Chronic; Brain Ischemia; Cell Count; Hippocampus; Male; Nerve Degeneration; Neurons; Quinoxalines; Rats; Rats, Inbred Strains; Receptors, AMPA; Receptors, Glutamate; Receptors, N-Methyl-D-Aspartate; Receptors, Neurotransmitter

Excitatory amino acids are implicated in the development of neuronal cell damage following periods of reversible cerebral ischemia or insulin-induced hypoglycemic coma. To explore the importance of glutamate receptor activation in the posthypoglycemic phase, we exposed rats to 20 min of insulin-induced severe hypoglycemia. The rats were treated immediately after the hypoglycemic insult with four regimes of glutamate receptor antagonists: (1) the AMPA (alpha-amino-3-hydroxy-5-methyl-4-isoxazole propriate)-receptor antagonist NBQX [2.3-dihydroxy-6-nitro-7-sulfamoyl-benzo (F) quinoxaline] given as a bolus dose of 30 mg.kg-1 i.p., followed by an i.v. infusion of 225 micrograms.kg-1.min-1 for 6 h; (2) the non-competitive NMDA-receptor antagonist, dizocilpine (MK-801) 1 mg.kg-1 given i.v.; (3) a combined NBQX treatment, (a bolus dose of 10 mg.kg-1 i.p., followed by an i.v. infusion of 225 micrograms.kg-1.min-1 for 6 h), with dizocilpine 0.33 mg.kg-1 given twice i.p. at 0 and 15 min after recovery and (4) the competitive NMDA-receptor blocker CGP 40,116 [D-(E)-2-amino-4-methyl-5-phosphono-3- pentenoic acid] 10 mg.kg-1 given i.p. In the striatum, all glutamate receptor blockers significantly decreased neuronal damage by approximately 30%. An approximately 50% decrease in neuronal damage was demonstrated in neocortex and hippocampus following the combined treatment with NBQX and dizocilpine, while protection was variable following the treatment with a single glutamate-receptor antagonist.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: 2-Amino-5-phosphonovalerate; Animals; Blood Pressure; Brain Ischemia; Cell Death; Dizocilpine Maleate; Electroencephalography; Excitatory Amino Acid Antagonists; Insulin Coma; Male; Necrosis; Neurons; Quinoxalines; Rats; Rats, Wistar; Receptors, AMPA; Receptors, N-Methyl-D-Aspartate

Central neuroexcitatory receptors (N-methyl-D-aspartate [NMDA], non-NMDA) may affect outcome from cerebral ischemia by altering sympathetic nervous system activity. We tested whether ketamine, an NMDA antagonist, and NBQX, a non-NMDA antagonist, improve outcome from incomplete cerebral ischemia in the rat and whether a change in outcome is related to changes in plasma catecholamines. There were five treatment groups: group 1 (control, n = 10) received a fentanyl infusion at a rate of 25 microgram.kg-1.h-1 and ventilation with 70% N2O in O2. Group 2 (n = 10) received the same anesthetic treatment and were given an intraperitoneal injection of 30 mg/kg NBQX 15 min prior to ischemia. Group 3 (n = 10) received a ketamine infusion of 1.0 mg.kg-1.min-1 and ventilation with room air. Group 4 (n = 10) received a ketamine infusion of 1.5 mg.kg-1.min-1. Group 5 received a ketamine infusion of 1 mg.kg-1.min-1 plus a 6 ml/kg intraperitoneal injection of 40% glucose solution 15 min before the start of ischemia. Ischemia was produced by right common carotid ligation combined with hemorrhagic hypotension to 35 mmHg for 30 min. Blood gases, pH, and skull temperature were controlled during ischemia. Plasma glucose increased during ischemia in all groups but was lower in ketamine-anesthetized rats (groups 3 and 4). Glucose-loaded ketamine-anesthetized rats (group 5) had plasma glucose concentrations similar to the control group. Plasma epinephrine and norepinephrine concentrations were significantly less in ketamine-anesthetized rats (groups 3, 4, and 5) during ischemia compared to controls (P less than 0.05). Neurologic outcome was significantly better (P less than 0.05) in all ketamine-treated rats (groups 3, 4, and 5) compared to the control group, regardless of plasma glucose concentration during ischemia. NBQX did not improve neurologic outcome. These results suggest that ketamine improves neurologic outcome from incomplete cerebral ischemia by a mechanism related to a decrease in plasma catecholamine activity.

Topics: Animals; Blood Glucose; Blood Pressure; Brain; Brain Ischemia; Cerebrovascular Circulation; Electroencephalography; Epinephrine; Fentanyl; Ketamine; Male; N-Methylaspartate; Norepinephrine; Oxygen Consumption; Quinoxalines; Rats; Rats, Inbred Strains

2,3-Dihydroxy-6-nitro-7-sulfamoyl-benzo(F)quinoxaline (NBQX) is an analog of the quinoxalinedione antagonists to the non-N-methyl-D-aspartate (non-NMDA) glutamate receptor. NBQX is a potent and selective inhibitor of binding to the quisqualate subtype of the glutamate receptor, with no activity at the NMDA and glycine sites. NBQX protects against global ischemia, even when administered 2 hours after an ischemic challenge.

Topics: alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; Animals; Aspartic Acid; Brain Ischemia; Cerebral Cortex; Hippocampus; Ibotenic Acid; In Vitro Techniques; Kainic Acid; N-Methylaspartate; Neurons; Oxadiazoles; Pyramidal Tracts; Quinoxalines; Quisqualic Acid; Rats; Receptors, Glutamate; Receptors, Kainic Acid; Receptors, Neurotransmitter