SPREADING DEPRESSION INDUCES DEPLETION OF MAP2 IN AREA CA3 OF THE HIPPOCAMPUS IN A RAT UNILATERAL CAROTID-ARTERY OCCLUSION MODEL

Traumatic brain injury (TBI) induces neuronal cell loss in area CA3 of the hippocampus, However, it has not yet been established why traumat ic injury of the cortex induces neuronal damage in more remote areas, Spreading depression (SD) may be one potential mechanism for this path ophysiology, The present study evaluated whether SD on the cortex evok es a pathological change in the hippocampus, Forty-two Fisher rats wer e assigned to four groups: Group I: sham operation (n = 7), Group II: right carotid occlusion (UO) for 7 days (n = 7), Group III: repeated i nduction of SD by KCI application on dura for 7 days (n = 7), Group II I' for 3 h (n = 7), Group IV: SD induction and UO for 7 days (n = 14) Group IV' for 3 h (n = 7), In 5 out of 7 animals in Groups III' and IV ', cerebral blood flow (CBF) was monitored using laser Doppler flowmet ry for 3 h during the passage of SD, The brains were processed for imm unohistochemical analysis of microtubule-associated protein 2 (MAP2). Reactive hyperemia induced by SD was not significantly suppressed by r ight carotid occlusion (194 +/- 25% and 181 +/- 42% UO in Groups III a nd IV, respectively), In 6 out of 7 animals in a 7-day model of Group IV, and 3 animals in a 7-day model of Group III, MAP2 depletion in the CA3 area of the hippocampus (partly including CA2) was observed, alth ough no change in the hippocampus was observed in other groups, In con clusion, SD in combination with UO yielded reproducible lesions in CA3 , Neuronal injury in the hippocampus after brain trauma may be attribu table to SD in combination with the blood flow restriction.