DELAYED VAGINAL OPENING IN RATS AFTER AN INTRAVENTRICULAR INJECTION OF 6-HYDROXYDOPAMINE

Abstract

In adult mammals, brain catecholamines participate in the central control of gonadotrophin release (for review, see Coppola, 1971). The rôle of brain amines in the process of puberty is less well understood. In the female rat, the first external sign of puberty, vaginal opening (VO), is closely associated with first ovulation and onset of vaginal cyclicity. This indicates that the cyclic release mechanism must become functional at or before that time. The drug 6-hydroxydopamine (6-OHDA) selectively impairs or destroys central catecholaminergic neurones after its injection into a brain ventricle (Malmfors & Thoenen, 1971), interferes with ovulation (Ruf, 1971), and prevents the compensatory release of gonadotrophins initiated by hemigonadectomy (Zolovick, 1972). In this study, we investigated the effect of 6-OHDA on VO in the pubescent rat to see whether the maturation of adrenergic inputs to hypothalamic peptidergic neurones may be a component of the pubertal process. About 250 female Sprague-Dawley rats,