MELATONIN RECEPTORS MEDIATE CONTRACTION OF A RAT CEREBRAL-ARTERY

MELATONIN receptors are expressed in the cerebral arteries of the rat which form the circle of Willis. We report here that melatonin induces contraction of in vitro preparations of pressurized rat posterior com municating artery, in a concentration-dependent manner. This action of melatonin is inhibited by S-20928, a specific melatonin receptor anta gonist. Our results demonstrate that the contractile action of melaton in is mediated by its receptors in the cerebral artery, and suggest a role for melatonin in the regulation of cerebral circulation.