In Vitro Method of Studying the Site of Action of Bromocryptine on Hypothalamus‐Pituitary‐Testis Function in Rats

The effects of bromocryptine, a specific dopaminergic agonist, were studied in vitro on the system comprising the hypothalamic tissue, the collagenase‐digested, isolated anterior pituitary cells, and the Leydig cells, by measuring the testosterone production of the Leydig cells. The in vitro testosterone production and the HCG sensitivity of the isolated Leydig cells decreased in the presence of 10‐5 M bromocryptine, whereas 10‐8–10‐6 M concentrations were ineffective. However, bromocryptine in concentrations of 10‐7–10‐6 M inhibited the isolated adenohypophyseal cell‐induced stimulation of the Leydig cells. The same inhibitory effect of bromocryptine was observed when the stimulation of the pituitary cell – Leydig cell system was induced by LHRH or hypothalamic tissue in vitro. Bromocryptine in a concentration of 10‐6 M did not alter the LHRH content and release of the hypothalamus measured by radioimmunoassay in the hypothalamic tissue and in the medium after an in vitro incubation. The results suggest an inhibitory effect of bromocryptine on the pituitarytestis axis by acting on the pituitary and testis levels in the in vitro system studied.