Internal and external carotid vascular responses to vasoactive agents in the monkey

Internal and external carotid blood flows in anesthetized monkeys were measured simultaneously using electromagnetic flowmeters. Complete dose-response relationships were established for the effects of intracarotid infusion of several humoral agents implicated in migraine. Both the internal and external carotid vasculatures were constricted by serotonin and prostaglandin F2alpha and dilated by bradykinin, histamine, and acetylcholine. Noradrenalin and adrenaline constricted the external carotid vasculature but had little direct effect in the internal carotid territory. Prostaglandin E1 dilated the external carotid vasculature. Low doses of prostaglandin E1 produced dilation in the internal carotid circulation, but with higher doses there was a paradoxical abolition of this effect.