The effect of testosterone on the release of endogenous catecholamines from the hypothalamus of the cockerel in vitro.

Castration of immature cockerels caused a significant rise in plasma luteinizing hormone concentrations. This effect was prevented by testosterone (T) replacement therapy. In vivo T replacement therapy reduced the release of endogenous catecholamines from hypothalamic tissue following in vitro incubation with high K+ artificial avian cerebrospinal fluid (ACSF). In vitro incubation with 500 nM T significantly reduced the release of endogenous catecholamines from hypothalamic tissue following incubation with high K+ ACSF. These results suggest that T can reduce the functional activities of catecholaminergic neurones in the hypothalamus and that these neurones may play a facilitatory role in the control of gonadotrophin secretion in the cockerel.