Rapid Naloxone-Induced Alterations of Androgen Variables in the Growing Male Rat

Publisher Website
Google Scholar
Abstract
Contrary to earlier views on the inability of naloxone to affect androgen variables by way of general circulation, systemically applied naloxone (2.5 mg/kg body weight, single i.p. or i.v injection) has been shown to rapidly induce (within an hour) a significant fall (–35,7% on the average) of the concentration of serum androgen (testosterone and dihydrotestosterone; (T + DHT) in peripubertal rats (51–58 days old). Such a response to the opiate antagonist was absent, however, in low-androgen prepubertal animals (37–44 days old) and in those among peripubertal rats which still showed subcritical initial levels of androgen in circulation (M). The possibility thus remains open that indirect inhibitory effects of injected naloxone may be operational in intact animals. Hypoprolactinemia, known to interfere in an age-dependent manner with the responsiveness of Leyding cells to luteinizing hormone (LH), may be of particular relevance: a significant fall of serum prolactin (PRL; -46%) has been regularly observed after systemic naloxone in those age groups which also responded to the opiate antagonist by a fall of circulating androgen and a decrease in basal in vitro steroidogenesis. A concomitant rise of serum LH has also been recorded after naloxone, but in all rats including the prepubertal group which did not respond with decreases of serum PRL and androgen.