Delayed treatment with YM90K, an AMPA receptor antagonist, protects against ischaemic damage after middle cerebral artery occlusion in rats

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 (2.5-20 mg kg(-1) h(-1) for 4 h) starting immediately after occlusion of the middle cerebral artery significantly reduced the cortical infarct volume 24 h 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 (20 mg kg(-1) h(-1) for 4 h) was delayed up to 2 h 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 1.13 mg kg(-1) was administered by intravenous bolus injection immediately after middle cerebral artery occlusion, followed by intravenous infusion at 0.785 mg kg(-1) h(-1) for 4 h (35% reduction, P < 0.05). This neuroprotective effect was not observed when administration was delayed Ih 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.