Blood flow through cerebral collateral vessels in hypertensive and normotensive rats

We tested the hypothesis that blood flow through cerebral collateral vessels is lower in stroke-prone spontaneously hypertensive rats (SHRSP) than in normotensive Wistar-Kyoto rats (WKY) after occlusion of the middle cerebral artery and during maximal vasodilatation. Cerebral blood flow, measured with microspheres, was similar in adult male SHRSP and WKY under control conditions. In both strains, occlusion of the middle cerebral artery reduced blood flow and vascular conductance to the territory of the occluded artery, as compared with homologous tissue on the side contralateral to the occlusion. The territory distal to the site of occlusion was identified by intravital demarcation with neutral red dye. In both strains, vasodilatation produced by seizures after occlusion of the middle cerebral artery produced minimal increases in blood flow to the territory of the occluded artery. Blood flow and vascular conductance to the territory of the occluded MCA were significantly lower in SHRSP than in WKY (p less than 0.05) after occlusion and during seizure after occlusion. We conclude that after occlusion of the middle cerebral artery, there is less blood flow through cerebral collateral vessels in SHRSP than in WKY. We speculate that the lower blood flow through collateral vessels in SHRSP may be related to structural differences in those vessels. Thus, the tendency toward infarction after occlusion of the middle cerebral artery in SHRSP may be related, at least in part, to a more limited dilator reserve of cerebral collateral vessels in SHRSP.