The cells responsible for the secretion of follicular stimulating hormone (fsh) and luteinizing hormone (lh) in the hypophysis of rats constitute two different populations (Hildebrand, Rennels & Finerty, 1957). These gonadotrophic cells are capable of synthesizing, storing and releasing their hormones independently. A number of pharmacological agents have been demonstrated to stimulate or block the release of pituitary gonadotrophins (Rennels, 1961; Sawyer, Critchlow & Barraclough, 1955). This communication describes an experiment concerning the differential effects of nalorphine on the release of pituitary gonadotrophins in male rat.
Male Long-Evans rats, 46 days old and weighing 200 g, were used in this study. Nalorphine hydrochloride dissolved in saline was injected subcutaneously (25 mg/kg) daily for a 2-week period. All nalorphine injections were given between noon and 14.00 hours. The control rats received an