RESUMEN
Exposure of male hamsters to short daily photoperiods (1 hour of light and 23 hours of darkness daily for 9 weeks led to total involution of the testes and accessory sex organs (seminal vesicles and coagulating glands). Pituitary levels of immunoreactive prolaction also decreased by about 60 percent after dark exposure. The inhibitory effects of darkness on the reproductive organs were prevented either by pinealectomy or by the subcutaneous implantation of a melatonin-beeswax pellet into the animals each week. Both pinealectomy and melatonin treatment also returned pituitary levels of prolactin toward normal. The results suggest that melatonin is not the pineal antigonadotrophic factor in the male golden hamster.
Asunto(s)
Gonadotropinas Hipofisarias/metabolismo , Glándula Pineal/fisiología , Animales , Peso Corporal , Ritmo Circadiano , Cricetinae , Oscuridad , Luz , Masculino , Melatonina/farmacología , Melatonina/fisiología , Tamaño de los Órganos , Glándula Pineal/efectos de los fármacos , Adenohipófisis/análisis , Prolactina/análisis , Prolactina/sangre , Prolactina/metabolismo , Próstata/anatomía & histología , Próstata/efectos de los fármacos , Radioinmunoensayo , Vesículas Seminales/anatomía & histología , Vesículas Seminales/efectos de los fármacos , Especificidad de la Especie , Testículo/anatomía & histología , Testículo/efectos de los fármacosRESUMEN
The pineal has been previously shown to be an important factor in the regulation of testicular function in photoperiodic mammals. The effects of lack or increase in pineal hormones on testicular hormonal receptors has, therefore, been examined. Pinealectomy decreased the concentration of testicular LH receptors in hamsters exposed to either a long or short photoperiod but had no effect on the concentration of testicular PRL receptors. In animals exposed to a short photoperiod, pinealectomy prevented testicular regression and the concomitant decreases in total LH and PRL receptor contents. Treatment for 12 weeks with either melatonin or 5-methoxytryptamine caused a decrease in testicular PRL receptor levels, whereas the only changes in LH receptor levels were due to melatonin-induced testicular regression. The present results indicate that some of the effects of pineal hormones on the testes are independent of the pineal-induced changes in testes mass and are the consequence of long-term action. Furthermore, testicular function appears to be affected by both the lack or the increase in pineal hormones.