The central vasomotor effects of 5-hydroxytryptamie.

In the dog, injection of 5-hydroxytryptamine into the cerebral ventricles caused hypotension, inhibition of the pressor response to occlusion of the carotid artery and inhibition of the pressor or depressor response evoked by electrical stimulation of the central end of the cut vagus. Hypotension and inhibition of the vagal vasomotor response also occurred in dogs in which the carotid sinuses had been denervated and the vagi cut. The site of action was central. Local cerebral vascular changes could not have been responsible for the action. The central vasomotor effects of 5-hydroxytryptamine are mediated through the sympathetic outflow. Implications of these findings are discussed in relation to the effects of intravenous 5-hydroxytryptamine and the mechanism of action of reserpine.