This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Copyright Permission Citing Articles Citing Articles via Google Scholar Google Scholar Articles by PAVEL, S. Articles by CALB, M. Search for Related Content PubMed PubMed Citation Articles by PAVEL, S. Articles by CALB, M.

Inhibition of Release of Corticotropin Releasing Hormone in Cats by Extremely Small Amounts of Vasotocin Injected into the Third Ventricle of the Brain. Evidence for the Involvement of 5-Hydroxytryptamine-Containing Neurons

institute of Endocrinology Bucharest, Rumania

Abstract

A single injection of 10^–6 pg synthetic arginine vasotocin (AVT), corresponding to about 600 molecules AVT, into the third ventricle of urethane-anesthetized cats, significantly decreased plasma cortisol levels between 15 and 60 min after the injection. A partially purified bovine pineal AVT injected into the third ventricle in an equivalent amount, produced the same effects. After incubation with trypsin, pineal AVT completely lost its ability to decrease plasma cortisol levels. In the range tested, the effects of synthetic AVT appear dose-dependent since 10^–5 pg caused a more pronounced effect than 10^–6 PG, and 10^–7 pg only slightly decreased plasma cortisol levels. Neither synthetic arginine vasopressin nor oxytocin, injected into the third ventricle in the amount of 10^–6 pg, was able to affect plasma cortisol levels. When 10^–6 pg of synthetic AVT was injected into the lateral ventricle of the brain, infundibular recess, or into the pituitary, no effect on plasma cortisol levels could be detected. Also, the same amount of synthetic AVT, injected into the third ventricle of cats treated 48 h earlier with pchlorophenylalanine (p-CPA), failed to decrease plasma cortisol levels. Administration of 5-hydroxytryptophan (5-HTP) to p-CPA-treated cats 1 h before the intraventricular injection of AVT partially restored the ability of AVT to decrease plasma cortisol levels. The hypothalamic 5-hydroxytryptamine (5-HT) content of cats increased significantly at 30 min after the injection of 10^–5 pg synthetic AVT into the third ventricle. The same amount of vasopressin or oxytocin injected into the third ventricle was unable to affect the hypothalamic 5-HT content. The increase of plasma cortisol levels induced by a crude corticotropin releasing factor (CRF) injected into the pituitary was not significantly affected by die previous intraventricular injection of AVT. It is concluded that AVT injected into the third ventricle of cats decreases plasma cortisol levels by inhibiting corticotropin releasing hormone (CRH) synthesis and/or release and that the mammalian brain contains the most sensitive receptors for AVT so far described. The hypothesis is advanced that these receptors are 5-HT containing neurons.

Received June 28, 1976.