Effects of testosterone on sexually dimorphic parvocellular neurons expressing vasotocin mRNA in the male quail brain

In situ hybridization with a P-33-labelled cDNA probe was used to analyze t he effects of castration and replacement therapy by testosterone on the num ber of neurons expressing vasotocin mRNA in the male quail brain. Castratio n completely eliminated neurons expressing vasotocin mRNA in the previously described parvocellular vasotocin cell groups, located in the medial preop tic nucleus and in the anterior and posterior part of the medial subdivisio n of the bed nucleus of the stria terminalis. These effects were completely reversed by a 3-week treatment with exogenous testosterone. No marked chan ge in vasotocin expression could be detected in the magnocellular cell grou ps located in the paraventricular and supraoptic nuclei. These data indicat e that the testosterone-induced changes in the vasotocinergic innervation o f the quail medial preoptic region and bed nucleus of the stria terminalis result from controlling mechanisms at the pretranslational, presumably tran scriptional level. These control mechanisms are therefore very similar to t hose described for the rat brain despite the existence of major differences in the neuroanatomical organization of this peptidergic system in the two species. (C) 1999 Elsevier Science B.V. All rights reserved.