Pieper D R
Endocrinology. 1984 Nov;115(5):1857-62. doi: 10.1210/endo-115-5-1857.
Maintenance of male golden hamsters on short photoperiod leads to testicular regression due to pineal gland-mediated inhibition of the hypothalamo-hypophyseal reproductive system. This study clarifies the dynamics of the action of GnRH at the pituitary level after short photoperiod-induced gonadal regression. In Exp 1, adult male golden hamsters were injected with BSA or varying doses of exogenous GnRH every 8 h for 3 days. There was no effect on the number of GnRH receptors, indicating that GnRH does not increase the number of its own receptors in hamsters as it does in rats. In Exp II, adult male golden hamsters were placed on a 14-h light, 10-h dark lighting schedule (LD 14:10) or LD 6:18. Nine weeks later, half of the animals on each photoperiod were castrated, and 10 weeks after initiation of the experiment, intact and castrated hamsters were decapitated. Intact hamsters on LD 6:18 had the expected reduction in serum LH levels and testicular weight compared to intact animals on LD 14:10. There was a postcastration rise in serum LH in both groups, but the increase was attenuated in the animals on short photoperiod. Castration of animals on LD 14:10 resulted in an increased number of GnRH receptors per pituitary, but this increase was at least partly due to an increase in pituitary weight. Intact animals on LD 6:18 had fewer pituitary GnRH receptors than intact hamsters on LD 14:10, but this decrease was not due solely to a decrease in pituitary weight. These results indicate that maintenance on short photoperiod results in a decreased number of pituitary GnRH receptors. In Exp III, intact animals on LD 6:18 responded to 1 microgram GnRH, sc, with an increment in LH secretion similar to that in intact animals on LD 14:10. Castration of animals on long photoperiod increased the LH response to GnRH, but castration of hamsters on short photoperiod did not. In conclusion, a reduced number of pituitary GnRH receptors may be involved in the testicular regression associated with short photoperiod in male golden hamsters.
将雄性金黄仓鼠饲养在短光照周期下会导致睾丸退化，这是由于松果体介导的对下丘脑 - 垂体生殖系统的抑制作用。本研究阐明了短光照周期诱导性腺退化后，GnRH在垂体水平的作用动态。在实验1中，成年雄性金黄仓鼠每8小时注射一次BSA或不同剂量的外源性GnRH，持续3天。这对GnRH受体数量没有影响，表明GnRH在仓鼠中不会像在大鼠中那样增加其自身受体的数量。在实验II中，成年雄性金黄仓鼠被置于14小时光照、10小时黑暗的光照周期（LD 14:10）或LD 6:18。九周后，每个光照周期的一半动物被阉割，实验开始10周后，完整和阉割的仓鼠被断头。与LD 14:10的完整动物相比，LD 6:18的完整仓鼠血清LH水平和睾丸重量出现预期的降低。两组动物阉割后血清LH均有升高，但短光照周期的动物升高幅度减弱。对LD 14:10的动物进行阉割导致每个垂体中GnRH受体数量增加，但这种增加至少部分是由于垂体重量增加。LD 6:18的完整动物比LD 14:10的完整仓鼠垂体GnRH受体少，但这种减少并非仅由于垂体重量降低。这些结果表明，饲养在短光照周期导致垂体GnRH受体数量减少。在实验III中，LD 6:18的完整动物皮下注射1微克GnRH后，LH分泌增加，与LD 14:10的完整动物相似。长光照周期动物阉割后增加了对GnRH的LH反应，但短光照周期仓鼠阉割后没有。总之，垂体GnRH受体数量减少可能与雄性金黄仓鼠短光照周期相关的睾丸退化有关。
