Metabolic and non-metabolic cerebrovasomotor mechanisms operational during hypertensive states of different origin in rats.

We attempted to elucidate the vasomotor mechanisms regulating the cerebral circulation of rats under arterial hypertensive states of different origin. Sudden cold exposure elicited a cerebrovasodilator response mediated primarily by an enhanced cerebral metabolic state. The response was not modified by the concomitantly enhanced cerebrovascular sympathetic action. Central inhibition of the baroreceptor reflex, as achieved by chemical inhibition of the caudal ventrolateral medulla, disinhibited a non-metabolic cerebrovasodilator mechanism. However, its action was masked by a concomitantly enhanced sympathetic vasoconstrictor action. Another type of cerebrovasodilator response, also of non-metabolic origin, was elicited by chemical stimulation of the defence area within the periaqueductal grey matter. Thus, the cerebrovasomotor mechanisms are diversely activated so as to cope adequately with the individual conditions imposed on the animals.