Neuroprotective effects depend on the model of focal ischemia following middle cerebral artery occlusion.

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.