Cerebrovascular injury and circuratory disturbances caused by platelet aggregation

Thirty rabbits were injected with 0.7mg/kg of sodium arachidonate into the right carotid artery to produce intravascular aggregation of platelets. Cerebral surface was observed through the skull window, and blood pressure, respiration, electrocardiogram and electroencephalogram were recorded continuously, platelet count and volume were studied before, immediately, 10, 30 and 60 minutes after the injection. Evans blue was injected 10minutes after the injection. One hour after, animals were perf used with formaldehyde or glutaraldehyde solution for light or scanning electron microscopic examination. Shortly after the injection, white thrombi were noticed in the vessels. Prominent blue staining of the brain were observed on the injected side. Histologically, extravasation of plasma substances from arteries, thick wall with convoluted internal elastic lamina and degeneration of the vascular walls were noticed on the injected side. The scanning electron micrograms showed disarrangement of arterial endothelial lining associated with remarkable platelet adhesion. The result suggests that intravascular aggregation of platelets produced not only the simple obstruction but constriction and damage of the cerebral arteries. The result suggests the paticipation of potent platelet aggregating and vasoconstricting substances, prostaglandin endoperoxides, thromboxane A2 and serotonin released from the activated platelets in the genesis of cerebral insufficiency.