CHRONIC CEREBRAL HYPOPERFUSION IN THE RAT - TEMPORAL DELINEATION OF EFFECTS AND THE IN-VITRO ISCHEMIC THRESHOLD

Acute reductions in cerebral blood flow of up to 50% do not affect neu ronal function although it has been shown that reductions of a similar magnitude maintained for 26 weeks do induce neuronal changes. In vitr o rat hippocampal LTP was evaluated after 10 weeks of cerebral hypoper fusion. An assessment was also made of the possible 'robustness' of hi ppocampal CA1 pyramidal neurons to combined in vitro hypoxic/ischemic insults because of previously shown differences in hemodynamic autoreg ulatory curves. No differences were found between controlled and chron ically hypoperfused animals in either study. It is concluded that the changes in neuronal function induced by reductions in cerebral blood f low of less than 50% take time to develop and do not induce adaptive c hanges in affected neurons. The mechanism for these changes remains to be elucidated.