✓ Alterations in cerebrovascular tone caused by the intracarotid administration of prostaglandin E1, A1, and F2a were evaluated by means of a standard perfusion technique in dogs and monkeys. Only PGF2a evoked a selective increase in cerebrovascular tone. This effect was observed in both species and resembled the action of serotonin. On the other hand, prostaglandin E1 selectively reduced cerebrovascular tone in dogs, but had no such specific action in the monkey. Prostaglandin A1 lacked a specific influence on the cerebral circulation of either species. Since different prostaglandins produced specific and diametrically opposite effects on cerebral circulation, these substances may be useful in experimental studies of vasospasm, and may normally influence cerebrovascular tone.
There is increasing evidence that platelets play a key role in the development of arterial occlusive lesions and in the tissue response to them. Direct evidence for a platelet contribution in experimental vascular occlusive stroke and subarachnoid hemorrhage was sought. Platelet counts were done on jugular blood before and after production of the vascular lesion. Craniectomy had little or no effect but occlusion or puncture of the middle cerebral artery invariably produced a prompt and striking fall in the platelet count of venous blood draining the affected side. Some implications of this observation are discussed.
✓ The occurrence of symptomatic carotid stenosis and asymptomatic ipsilateral intracranial aneurysm is reported. The successful management by planned staged surgical treatment of both lesions is discussed.
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