Mechanisms of suppression of gonadotropins secretion during lactation in the rat.

研究了大鼠哺乳期抑制卵泡刺激素(FSH)和黄体生成素(LH)分泌的机制。在整个哺乳过程中，大鼠的血浆FSH水平相对稳定，无论产仔的大小，尽管哺育8只幼鼠的母鼠的促黄体生成素水平始终低于哺育2只幼崽的母鼠。卵泡退行性变与血浆促黄体生成素水平下降相对应，卵泡成熟时基础促黄体生成素水平升高。抑制素活性和血浆雌二醇-17-β-GT；水平也是如此。1985年的研究结果表明，哺乳8只幼鼠的FSH分泌在哺乳期的前半段主要受哺乳神经刺激的抑制，而不是卵巢抑制素。然而，来自Graafian卵泡的抑制素可能在哺育8只幼鼠的哺乳期后半段和哺育…的大鼠的整个哺乳期抑制FSH的分泌起主要作用由于内源性阿片肽和促肾上腺皮质激素释放因子(CRF)在哺乳过程中被激活，并在中央注射时降低黄体生成素水平，我探索了这些多肽在哺乳诱导的促黄体生成素和卵泡刺激素分泌抑制中的作用。去势哺乳期大鼠去卵巢两天后，侧脑室注射微量促黄体生成素或β-内啡肽，30分钟内可迅速抑制黄体生成素的分泌。而FSH水平则在注射后6h及以后下降。重复一次静脉注射。每隔6h注射CRF或β-内啡肽，不仅能引起哺乳期大鼠黄体生成素的分泌，还能引起卵泡刺激素的分泌。中枢注射β-内啡肽后，血浆催乳素水平在30分钟内显著升高，而CRF则无明显影响。这些观察表明，CRF和β-内啡肽通过脑作用部位对哺乳期大鼠的促黄体生成素和促卵泡激素分泌产生有害作用。因此，中枢CRF/β-GT；-内啡肽途径的激活可能在哺乳诱导的促黄体生成素和卵泡刺激素分泌抑制中起重要作用。较少

Mechanisms responsible for suppression of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) secretion during lactation were investigated in rats. Throught lactation in rats plasma levels of FSH were relatively constant regardless of the litter size though LH levels were consistently lower in dams nursing 8 pups than in dams nursing 2 pups. Changes in follicular degeneration corresponded with the decrease of plasma LH and follicular maturation was noted with an increase in basal levels of LH. It is also true for inhibin activity and plasma levels of estradiol-17 <beta> . Findings in 1985 indicate that the neural stimulus of suckling rather than ovarian inhibin is mainly responsible for suppression of FSH secretion during the first half of lactation in rats nursing 8 pups. However, inhibin from Graafian follicles may play a primary role in the suppression of FSH secretion during the second half of lactation in rats nursing 8 pups and throughout lactation in the rats nursing … More 2 pups.Because endogenous opioid peptides and corticotropin releasing factor (CRF) are activated during suckling and decrease LH levels when injected centrally, I have explored the roles of these peptides in the suckling-induced inhibition of LH and FSH secretion. The acute administration of 10 <micro> g CRF or <beta> -endorphin into the lateral ventricle of ovariectomized lactating rats two days after removal of the litter caused a rapid inhibition of LH secretion within 30 min. On the other hand, levels of FSH were decreased 6 h after the injection and thereafter. Repeated i.c.v. injection of CRF or <beta> -endorphin at 6 h intervals caused not only LH secretion but also FSH secretion in lactating rats. The central administration of <beta> -endorphin caused a dramatic increase in levels of prolactin in the plasma within 30 min, whereas CRF showed no effect. Such observations suggest that CRF and <beta> -endorphin exerts deleterious action on the inhibition of LH and FSH secretion in lactating rats through brain sites of action. Therefore, it is possible that the activation of the central CRF/ <beta> -endorphin pathway may play an important role in the suckling-induced inhibition of LH and FSH secretion. Less