STRAIN DIFFERENCES IN VULNERABILITY OF HIPPOCAMPAL-NEURONS TO TRANSIENT CEREBRAL-ISCHEMIA IN THE RAT

Strain differences in the vulnerability of hippocampal neurons to an i schaemic insult were investigated in Sprague-Dawley, Wistar and Fische r 344 rats. Transient global brain ischaemia was produced for 5 minute s by a combination of bilateral carotid artery occlusion and oligaemic hypotension (40 mmHg) induced by exsanguination. The number of viable neurons in the CA1 subfield was counted under a light microscope 7 da ys after the ischaemic insult. The density of viable neurons in the CA 1 subfield of normal rats was around 150 cells/mm of CA1 length in all the strains examined; after global brain ischaemia, this parameter in Sprague-Dawley, Wistar and Fischer 344 strain rats was approximately 110, 120, and 70, respectively. The results suggest that the hippocamp al CAI neurons of Fischer 344 strain rats are more vulnerable to ischa emic insult than those of the other strains. There were many F344 rats (8/21) which showed atypical vasculature patterns in the posterior re gion of the circle of Willis, suggesting less blood flow through anast omosis from basilar artery to posterior cerebral artery and/or ill-bal anced blood flow between left and right hemispheres. These anatomical variations in the circle of Willis may in part contribute to the strai n differences in the vulnerability to cerebral ischaemia.