Glass J D, Dolan P L
Department of Biological Sciences, Kent State University, Ohio 44242.
Proc Soc Exp Biol Med. 1988 Jul;188(3):375-80. doi: 10.3181/00379727-188-42750.
A melatonin-induced supersensitivity of the gonadotropin-secretory system to the negative feedback action of sex steroids is thought to be important to the timing of seasonal reproduction. However, little is known concerning this action of melatonin. In the present study the antigonadal action of melatonin in the anterior hypothalamus (AH) of the white-footed mouse, Peromyscus leucopus, was used to examine the neuroendocrine mechanism whereby melatonin enhances the sensitivity to sex steroid negative feedback. Mice received a melatonin-containing pellet in the AH for 14 weeks, at which time they were castrated and treated sc with a Silastic testosterone (T) capsule for 3 weeks. At the time of castration, weight of the testes and the concentration of T in the blood of mice with a melatonin pellet were greatly reduced compared to mice with a blank (melatonin-free) implant in the AH (P less than 0.01). In mice treated with melatonin the physiological dose of T significantly reduced the concentrations of LH in blood and pituitary (P less than 0.05). This dose of T, however, had little effect on LH in mice with a blank pellet in the AH. Melatonin in the AH markedly increased the content of gonadotropin-releasing hormone (GnRH) in the mediobasal hypothalamus (P less than 0.05) in mice treated with T; however, there was little effect of melatonin and/or T in any other region examined. Melatonin and T had little effect on the contents of immunoreactive beta-endorphin (B-EP) in the hypothalamus, but T alone increased the content of B-EP in the preoptic area. These results are evidence that melatonin and T act in concert to induce the reproductively-quiescent state by suppressing secretion of GnRH from the hypothalamus.
褪黑素诱导促性腺激素分泌系统对性类固醇负反馈作用的超敏感性被认为对季节性繁殖的时间安排很重要。然而，关于褪黑素的这一作用却知之甚少。在本研究中，利用白足鼠（白足鼠属）下丘脑前部（AH）中褪黑素的抗性腺作用来研究褪黑素增强对性类固醇负反馈敏感性的神经内分泌机制。小鼠在AH中植入含褪黑素的小球14周，之后进行阉割，并皮下植入Silastic睾酮（T）胶囊3周。在阉割时，与AH中植入空白（不含褪黑素）小球的小鼠相比，植入褪黑素小球的小鼠睾丸重量和血液中T浓度大幅降低（P<0.01）。在接受褪黑素处理的小鼠中，生理剂量的T显著降低了血液和垂体中LH的浓度（P<0.05）。然而，该剂量的T对AH中植入空白小球的小鼠的LH几乎没有影响。在接受T处理的小鼠中，AH中的褪黑素显著增加了下丘脑中间基底部促性腺激素释放激素（GnRH）的含量（P<0.05）；然而，在检测的任何其他区域，褪黑素和/或T几乎没有影响。褪黑素和T对下丘脑免疫反应性β-内啡肽（B-EP）的含量几乎没有影响，但单独使用T可增加视前区B-EP的含量。这些结果证明，褪黑素和T协同作用，通过抑制下丘脑GnRH的分泌来诱导生殖静止状态。
