Vasopressin release induced by intracranial injection of eledoisin is mediated by central angiotensin II.

Pulse intracerebroventricular injection of eledoisin, but not of substance P, markedly increases plasma vasopressin levels in the rat. Intracerebroventricular pretreatment with sarcosine1, alanine8-angiotensin II, 1 microgram/rat, completely suppresses the effect of eledoisin, suggesting that it is mediated by angiotensin release and angiotensin II receptor activation. The vasopressin releasing effect of eledoisin is neither due to peripheral haemodynamic alterations, nor to activation of the peripheral renin-angiotensin system. It is apparently related to central angiotensin release in a specific neuronal pathway subserving vasopressin release. This effect is not secondary to inhibition by tachykinins of the brain mechanisms for angiotensin-induced drinking, but is probably expression of direct activation of specific tachykinin receptors controlling vasopressin release.