Modulatory Action of Testosterone on Morphine-Induced Changes of Mice Brain Prolactin

Interactions between sex hormones and opioid system in the brain may play a functional role in the regulation of pituitary hormone release in animals. In this study the effect of chronic administration of morphine on the brain levels of prolactin in gonadectomized and testosterone treated mice were examined. Castration of male animals caused a reduction of about 90% in the brain level of prolactin as compared to that of intact animals. Moreover administration of increasing doses of morphine (40 to 100 mg/kg) for a period of 9 days resulted in a reduction of 30% in the prolactin level in both intact and gonadectomized mice. However administration of testosterone to gonadectomized morphine treated animals resulted in a significant increase (about 40%) in brain prolactin level as compared with control values.
It is suggested that testosterone at its physiological concentration may not be involved in modulatory action of morphine on prolactin secretion, whereas there is a significant interaction between testosterone and opiates for modulation of prolactin secretion when the testosterone concentration is higher than physiological level.