The effect of serotonin on cerebral and extracerebral blood flow with possible implications in migraine

Serotonin (1 μg/kg/min) was infused into the internal or the external carotid artery in anaesthetised baboons. Blood flow through the carotid arteries was measured by electromagnetic flow probes. Cerebral blood flow was measured by the 133Xenon clearance method. Temporal muscle blood flow was measured from the clearance of 133Xenon following local injection into the muscle. The following results of the infusion of Serotonin were noted: 1) The blood flow through the external carotid artery and the temporal muscle increased by several hundred per cent. 2) The blood flow through the internal carotid artery was reduced by 57 %. 3) The cerebral blood flow was reduced by 17 % at normocapnia but by twice this figure at hypercapnia.