Selective platelet deposition during focal cerebral ischemia in the monkey

Platelet thrombosis in the microcirculation may play a central role in focal cerebral ischemia. The authors investigated platelet deposition after temporary middle cerebral artery (MCA) occlusion in the monkey. Anesthetized monkeys were infused with autologous 111In-labeled platelets and 51Cr-labeled red cells in order to measure platelet deposition independent of hemorrhage. The right MCA was occluded for 6 hrs with a clip via a trans-orbital approach. Following clip removal, reperfusion was carried out for 45 min after which the animal was sacrificed. Brain samples were assayed for platelet deposition in selected areas of the right and left hemispheres (RH, LH). Net platelet deposition was determined from the excess 111In counts above that contained in blood (as determined by 51Cr counts). It was found that ischemia resulted in selective platelet deposition in the area of the occluded MCA, i.e. the RH versus the corresponding areas in the LH. Differences between the RH and the LH were found in the (1) caudate nucleus, (2) internal capsule and (3) putamen. The data suggest that focal ischemia is associated with the activation of platelets in the ischemic area