Villanua M A, Agrasal C, Tresguerres J A, Vaughan M K, Esquifino A I
Departmento de Fisiología y Bioquímica, Facultad de Medicina, Universidad Complutense, Madrid, Spain.
J Pineal Res. 1989;6(1):33-41. doi: 10.1111/j.1600-079x.1989.tb00400.x.
Melatonin influences prolactin (PRL) secretion through unknown mechanisms. This work was undertaken to study the effects of melatonin administration on PRL secretion in pituitary-grafted male rats. Melatonin administration 5 hours before dark resulted in a marked decrease of previously high basal plasma PRL levels in pituitary-grafted rats, whereas a marked increase was detected in sham-operated animals. Vehicle treatment did not modify basal PRL values in grafted or sham-operated animals. Luteinizing hormone-releasing hormone (LHRH) administration resulted in a marked decrease of plasma PRL levels in vehicle-treated, sham-operated or grafted rats, as well as in melatonin-treated sham-operated rats. An increase in PRL levels was shown in grafted rats treated with melatonin. Estradiol benzoate (EB) administration resulted in an increase in plasma PRL levels both in sham-operated and grafted vehicle-treated rats. No PRL response could be detected in sham-operated, melatonin-treated animals after EB administration. In pituitary-grafted animals given melatonin, PRL response to EB administration was slight and delayed. From these data, melatonin appears to modify PRL secretion through multiple complex mechanisms that may depend on the physiological status (hormonal and neurotransmitter) of the animals. A direct effect at the pituitary level altering lactotroph sensitivity seems to be one plausible explanation for the current findings, although an hypothalamic site of action cannot be excluded.
褪黑素通过未知机制影响催乳素（PRL）的分泌。本研究旨在探讨给予褪黑素对垂体移植雄性大鼠PRL分泌的影响。在天黑前5小时给予褪黑素，可使垂体移植大鼠先前较高的基础血浆PRL水平显著降低，而在假手术动物中则检测到显著升高。给予赋形剂处理对移植或假手术动物的基础PRL值无影响。给予促黄体生成素释放激素（LHRH）可使给予赋形剂处理的、假手术或移植的大鼠以及给予褪黑素处理的假手术大鼠的血浆PRL水平显著降低。给予褪黑素处理的移植大鼠的PRL水平升高。给予苯甲酸雌二醇（EB）可使假手术和移植的给予赋形剂处理的大鼠的血浆PRL水平升高。给予EB后，在给予褪黑素处理的假手术动物中未检测到PRL反应。在给予褪黑素的垂体移植动物中，PRL对EB给药的反应轻微且延迟。根据这些数据，褪黑素似乎通过多种复杂机制调节PRL分泌，这些机制可能取决于动物的生理状态（激素和神经递质）。尽管不能排除下丘脑的作用部位，但垂体水平的直接作用改变催乳细胞敏感性似乎是对当前研究结果的一个合理的解释。
