6-(1h-imidazol-1-yl)-7-nitro-2-3(1h-4h)-quinoxalinedione and Brain-Ischemia

The spatial memory impairment and expression of apoptotic cells in hippocampal CA1 cells were investigated in rats using single and repeated ischemia models. The neuroprotective and memory-improving effect of YM-90K, an alpha-amino-3-hydroxy-5-methyl-isoxazole-4-propionate (AMPA) receptor antagonist, was compared to MK-801, an N-methyl-D-aspartate (NMDA) receptor antagonist. Twice-repeated ischemia, but not single ischemia, impaired the spatial memory and increased expression of apoptotic cells. YM-90K, given before and 6 h after the second reperfusion, significantly improved the memory and reduced the apoptotic cells 7 days after the second reperfusion in repeated ischemia. MK-801 neither improved the spatial memory nor reduced apoptotic cells. The present study showed that delayed expression of apoptotic cells is mediated by mechanisms involving AMPA receptors, but not by NMDA receptor, during the late phase after reperfusion. YM-90K could provide neuroprotective activity and improve the spatial memory impaired by repeated ischemia.

Topics: Animals; Apoptosis; Brain Ischemia; Disease Models, Animal; Dizocilpine Maleate; Excitatory Amino Acid Antagonists; Hippocampus; Male; Maze Learning; Memory Disorders; Nerve Degeneration; Neurons; Neuroprotective Agents; Quinoxalines; Rats; Rats, Wistar; Receptors, AMPA; Receptors, N-Methyl-D-Aspartate; Recovery of Function; Reperfusion Injury

By analyzing histological damages and the regional N-acetylaspartate (NAA) level simultaneously, we evaluated the effect of an alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA)/kainate receptor antagonist, YM90K [6-(1H-imidazol-1-yl)-7-nitro-2,3-(1H,4H)-quinoxalinedione monohydrochloride], in unilateral forebrain ischemia in gerbils. The right common carotid artery was clipped for 5 min under ether anesthesia, and reperfused for 7 days. The frozen brain sections were lyophilized and the hippocampal CA1 area was dissected out for HPLC assay of NAA. An adjacent section was stained with hematoxylin-eosin for counting survived neurons per 1 mm pyramidal layer of the hippocampal CA1 area. Postischemic administration of YM90K at 20 mg/kg and 25 mg/kg attenuated the decrease of both the number of survived neurons and the NAA level on the ischemic side in a dose-dependent manner. A significant linear correlation was observed between the NAA level and the number of intact neurons. These results indicated that the NAA level could be used as an index of neuroprotective effects of pharmacological agents in global cerebral ischemia.

Topics: Animals; Aspartic Acid; Brain Ischemia; Chromatography, High Pressure Liquid; Excitatory Amino Acid Antagonists; Gerbillinae; Hippocampus; Male; Prosencephalon; Quinoxalines; Receptors, AMPA; Receptors, Kainic Acid

An in vitro model of ischemia was developed and characterized using the acute rat hippocampal slice preparation. Neuroprotective concentrations of several competitive and noncompetitive glutamate subtype-selective antagonists (CGS-19755, MK-801, YM90K and GYKI-52466) were initially determined in anoxia-enhanced agonist-induced excitotoxicity experiments. Concentrations which proved to be effective in these studies were subsequently tested for their effectiveness against an ischemic episode. Ischemia was defined as a 30-min exposure to aglycemic media ending in 5 min of concurrent anoxia, a protocol which was arrived at by empirically determining the effect of various hypoglycemic and anoxic insults on the ability of hippocampal slices to retain their electrophysiological viability. Exposure to such an ischemic episode resulted in a loss of viability by most slices, an effect which was strongly dependent on extracellular calcium. AMPA antagonists applied alone produced no neuroprotective effect in the present model of in vitro ischemia, while NMDA antagonists applied alone had a modest neuroprotective effect. In contrast, the coapplication of 10 microM MK-801 and 300 microM GYKI-52466, noncompetitive NMDA and AMPA receptor antagonists, respectively, resulted in almost complete neuroprotection. This protection was comparable to that obtained by withholding extracellular calcium, indicating that the toxic effects of glutamate receptor overstimulation can be accounted for solely by calcium influx. The effect of this combination treatment on the survival rate of hippocampal slices was synergistic, that is greater than the sum of the effects of the individual compounds. The results indicate that neuroprotection against acute ischemic insults may require a combination therapy approach.

Topics: Animals; Anti-Anxiety Agents; Benzodiazepines; Brain Ischemia; Dizocilpine Maleate; Excitatory Amino Acid Antagonists; Hypoxia; Male; Neuroprotective Agents; Pipecolic Acids; Quinoxalines; Rats; Rats, Wistar; Receptors, AMPA; Receptors, N-Methyl-D-Aspartate

The neuroprotective effect of an alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) receptor antagonist YM90K [6-(1H-imidazol-1-yl)-7-nitro-2,3(1H,4H)-quinoxalinedione monohydrochloride] has been examined in a rat middle cerebral artery occlusion model. Intravenous infusion of YM90K (2.5-20mgkg(-l)h(-l) for 4h) starting immediately after occlusion of the middle cerebral artery significantly reduced the cortical infarct volume 24h after occlusion compared with the control group. The protection at the highest dose was 39% (P < 0.05). Similar protective effects were observed when YM90K (20mgkg(-1)h(-1) for 4h) was delayed up to 2h after middle cerebral artery occlusion (45% reduction, P < 0.05). CNS1102 [N-(1-naphthyl)-N'-(3-ethylphenyl)-N'-methylguanidine hydrochloride], a non-competitive N-methyl-D-aspartate (NMDA) receptor antagonist, also reduced the cortical infarct volume when 1.13mgkg(-1) was administered by intravenous bolus injection immediately after middle cerebral artery occlusion, followed by intravenous infusion at 0.785mgkg(-l)h(-1) for 4h (35% reduction, P<0.05). This neuroprotective effect was not observed when administration was delayed lh after middle cerebral artery occlusion. These results suggest that AMPA receptors might play a more important role than NMDA receptors in the late development of neuronal cell damage after focal cerebral ischaemia and that AMPA receptor blockade would be one beneficial strategy in treating acute stroke.

Topics: Animals; Brain Ischemia; Cerebral Arteries; Dose-Response Relationship, Drug; Guanidines; Injections, Intravenous; Male; Neuroprotective Agents; Quinoxalines; Rats; Rats, Inbred F344; Receptors, AMPA; Receptors, N-Methyl-D-Aspartate; Time Factors

The neuroprotective effect of YM90K, a potent AMPA receptor antagonist, was examined in rats with permanent and transient occlusion of middle cerebral artery (MCA) using intraluminal suture occlusion method. In rats with permanent MCA occlusions, two types of occluders were used to compare the efficacy of YM90K. When a 4-0 (diameter: 0.19 mm) suture was used, YM90K (20 mg kg(-1) h(-1) i.v. infusion for 4 h) significantly reduced infarct volume (P<0.05) and neurologic deficits (P<0.05) 24 h after MCA occlusion. Infarct volume was also reduced by YM90K at the same dose (P<0.01) when severe ischemia was induced by a 3-0 (diameter: 0.23 mm) suture. In rats with transient (3 h) MCA occlusions, a 10-mg kg(-1) h(-1) dose of YM90K that did not show significant protection in rats with permanent MCA occlusion offered neuroprotective effects. These data demonstrate that YM90K provides cerebral neuroprotection against a wide range of ischemic insults.

Topics: Animals; Arterial Occlusive Diseases; Brain; Brain Ischemia; Cerebral Arteries; Cerebral Infarction; Male; Neuroprotective Agents; Quinoxalines; Rats; Rats, Sprague-Dawley; Receptors, AMPA

The purpose of the present study was to compare the characteristics of the photochemical-induced thrombotic occlusion model and the thermocoagulated occlusion model of the middle cerebral artery in rats. We evaluated the neuroprotective effects of a NMDA receptor antagonist, (+)-MK-801 (dizocilpine, (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cycloheptan-5,10-imine), an alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptor antagonist, YM90K (6-(1H-imidazol-1-yl)-7-nitro-2,3(1H,4H)-quinoxalinedione monohydrochloride), a Ca2+ channel antagonist, S-312-d (S-(+)-methyl-4,7-dihydro-3-isobutyl-6-methyl-4-(3-nitrophenyl)-thieno[2 ,3-b]pyridine-5-carboxylate), the radical scavengers, MCI-186 (3-methyl-1-phenyl-2-pyrazolin-5-one) and EPC-K1 (L-ascorbic acid 2-[3,4-dihydro-2,5,7,8-tetramethyl-2-(4,8,12-trimethyl-tridecyl)-2H-1-be nzopyran-6yl-hydrogen phosphate] potassium salt), and a calcineurin inhibitor, FK506 (tacrolimus, Prograf). Although all tested agents in the present study attenuated the brain damage in the photochemical-induced thrombotic occlusion model, the radical scavengers did not attenuate the brain damage in the thermocoagulated occlusion model. The time course of brain damage and brain edema formation in the two models was examined. The time course of brain damage was not different in the two models, but the time course of brain edema was quite different. Brain edema formation in the photochemical-induced thrombotic occlusion model was significantly greater (P < 0.01) than that in the thermocoagulated occlusion model at all time point studied until 24 h after occlusion of the middle cerebral artery. The present study suggests that the photochemical-induced thrombotic occlusion model has characteristics of both permanent ischemia and ischemia-reperfusion.

Topics: Animals; Brain Edema; Brain Ischemia; Disease Models, Animal; Dizocilpine Maleate; Electrocoagulation; Immunosuppressive Agents; Injections, Intraperitoneal; Injections, Intravenous; Intracranial Embolism and Thrombosis; Male; Neuroprotective Agents; Quinoxalines; Rats; Rats, Sprague-Dawley; Tacrolimus

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

We investigated the pharmacological properties and neuroprotective actions of a novel alpha-amino-3-hydroxy-5-methylisoxazole-y-propionate (AMPA)/kainate receptor antagonist, [6-(1H-imidazol-1-yl)-7-nitro-2,3-(1H,4H)-quinoxalinedione hydrochloride (YM90K); formerly YM900], in comparison with those of 2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo(f)quinoxaline (NBQX). YM90K selectively displaced [3H]-AMPA binding (Ki = 0.084 microM) and was less potent in inhibiting [3H]-kainate (Ki = 2.2 microM), [3H]-L-glutamate (N-methyl-D-aspartate-sensitive site; Ki > 100 microM) and [3H]-glycine (strychnine-insensitive site; Ki = 37 microM) binding to rat brain membranes. YM90K co-injected with AMPA or kainate into the rat striatum protected cholinergic neurons against AMPA- or kainate-induced neurotoxicity. YM90K showed potent suppressive activity against audiogenic seizure in DBA/2 mice; ED50 values of YM90K and NBQX against tonic seizure were 2.54 and 7.17 mg/kg (i.p.), respectively. The duration of the anticonvulsant effects of YM90K and NBQX was 30 min, indicating that both compounds possess short action. In a global ischemia model, YM90K (15 mg/kg i.p. x 3), NBQX (30 mg/kg i.p. x 3) and CNQX (60 mg/kg i.p. x 3) significantly prevented the delayed neuronal death in the hippocampal CA1 region in Mongolian gerbils when administered 1 h after 5-min ischemia. In addition, the therapeutic time window for the neuroprotective effect of YM90K (30 mg/kg i.p. x 3) was 6 h. In a focal ischemia model, YM90K (30 mg/kg i.v. bolus+10 mg/kg/h for 4 h) reduced the volume of ischemic damage in the cerebral cortex in F344 rats. Thus, YM90K was shown to be a potent and selective antagonist for AMPA/kainate receptors in vitro and in vivo. This compound may provide a therapeutic effect in various neurodegenerative disorders such as ischemic stroke in which glutamate neurotoxicity is thought to play a critical role in neuronal damage.

Topics: Animals; Anticonvulsants; Brain Ischemia; Cerebral Infarction; Corpus Striatum; Gerbillinae; Ischemia; Male; Mice; Mice, Inbred DBA; Quinoxalines; Radioligand Assay; Rats; Rats, Inbred F344; Rats, Wistar; Receptors, AMPA; Receptors, Kainic Acid; Seizures