Drinking behaviour induced by intracerebroventricular administration of enkephalins to rats

Abstract

INTRACRANIAL administration of substance P to rats inhibits drinking induced by water deprivation, sodium-chloride load, and intracerebroventricular (i.c.) injection of angiotensin II or carbachol1. It has been suggested that substance P is a neurotransmitter used in primary afferent fibres terminating in the spinal cord2–4, but recent findings suggest also that, at least in mice, substance P may release endogenous opioids and thus produce analgesia5. If cerebral effects of substance P are, at least in part, due to the release of endogenous opioids, these substances might also possess an antidipsogenic effect. We describe here experiments in which we observed that enkephalins administered into the lateral ventricles of rats inhibited drinking induced by water deprivation or by i.c. injection of angiotensin II. We thus provide evidence that enkephalins have a potent and reproducible antidipsogenic effect in the rat.