CEREBROVASCULAR ADAPTATION AFTER UNILATERAL CAROTID-ARTERY LIGATION IN THE RAT - PRESERVATION OF BLOOD-FLOW AND ATP DURING FOREBRAIN ISCHEMIA

To investigate long-term adaptations after unilateral carotid artery l igation, the effect of forebrain ischemia on cerebral blood flow and A TP levels was determined at various times after ligation, Unilateral c arotid artery ligation was performed in male Wistar rats 0, 3, or 7 da ys before forebrain ischemia. Laser-Doppler blood flow was monitored b ilaterally over the parietal cortex and ATP was measured in the subadj acent cortex of both hemispheres at the end of a 10-minute episode of ischemia. In the 0-day group, forebrain ischemia reduced cortical bloo d flow to 12% +/- 8% (mean +/- SD) of preischemic values and lowered c ortical ATP to 26% +/- 35% of control levels in the ipsilateral hemisp here. Delaying the onset of forebrain ischemia for 3 days after caroti d artery ligation significantly improved cortical blood flow (29% +/- 12%, P < 0.05) and ATP levels (92% +/- 11%, P < 0.05) in the ipsilater al hemisphere. Delaying forebrain ischemia for 7 days also significant ly improved ipsilateral blond flow (36% +/- 11%, P < 0.05) and ATP lev els (81% +/- 29%, P < 0.05) compared with the 0-day group. In the cont ralateral hemisphere. the reduction in blood flow and ATP levels was n ot significantly altered by delaying the onset of forebrain ischemia f or 3 or 7 days, These results show that unilateral carotid artery liga tion induces longterm vascular adaptations that improve the collateral circulation and preserve ATP levels during a subsequent episode of is chemia.