Effects of morphine sulphate on pituitary-testicular morphology of rats

Morphine sulphate was administered, buy s.c. injection, to male rats at 50 mg/kg/day for up to 9 weeks. Control rats were given s.c. injections of sterile water. Serum luteinising hormone (LH) and testosterone concentrations and the weight and morphology of testes, pituitary glands and secondary sex organs were examined after 4 and 9 weeks' morphine treatment and also 13 weeks after dosing stopped. Treatment with morphine decreased serum LH and testosterone concentrations and reduced secondary sex organ weights. Differential staining techniques revealed modified secretory activity of pituitary gonadotrophic cells. All stages of spermatogenesis were found in testicular sections, but quantitative reductions in spermatogenic cell populations were found among morphine-treated rats. All the observed effects were reversed within 13 weeks of drug withdrawal. These findings are discussed in relation to existing knowledge of the hormonal control of spermatogenesis in rats.