OBJECTIVES: These studies are directed at clarification of factors that regulate cerebral blood flow and flow through aortic vasa vasorum. Specific goals this year were 1) to determine whether cutting sympathetic nerves to cerebral vessels produces stroke in hypertensive rats; 2) to determine whether stimulation or interruption of cholinergic pathways to cerebral vessels alters regulation of cerebral blood flow; 3) to determine whether increases in intracranial pressure produce redistribution of cerebral blood flow and whether sympathetic nerves contribute to this effect. The most significant achievement this year was the finding that sympathetic denervation predisposes to stroke in the presence of chronic hypertension is an important step in clarification of the physiological role of neural control in the cerebral circulation. This observation may be of importance to physicians who provide care to patients with hypertension and in prevention of stroke. Research goals for the coming year are to answer these questions: 1) Does sympathetic stimulation produce a shift in segmental resistance of cerebral resistance vessels by constricting large arteries but dilating small vessels? 2) Does physiological activation of sympathetic pathways affect cerebral blood flow? 3) Is the greater superficial petrosal nerve the primary source of cholinergic innervation of cerebral vessels?