Kennaway D J, Peek J C, Gilmore T A, Royles P
J Reprod Fertil. 1986 Sep;78(1):137-48. doi: 10.1530/jrf.0.0780137.
Prepubertal ewe lambs were treated with empty or filled melatonin implants. The implants were placed s.c. at birth and pituitary responsiveness to various doses of LHRH, LH/FSH pulsatility and prolactin and melatonin secretion were examined at 10, 19, 28, 36 and 45 weeks of age. Control animals (N = 10) showed no consistent alteration in pituitary responsiveness to LHRH during development. Ewes treated with melatonin (N = 10) had puberty onset delayed by 4 weeks (P less than 0.03) but no effect of melatonin on LH or FSH response to LHRH injection was observed at any stage of development. In the control and melatonin-treated ewe lambs the responses to LHRH injection were lower during darkness than during the day at all stages of development. No consistent differences in LH or FSH pulsatility were observed between treatment groups or during development. Prolactin concentrations, however, failed to decrease at the time of puberty (autumn) in the melatonin-treated group. Melatonin-treated ewe lambs maintained normal rhythmic melatonin production which was superimposed on a higher basal concentration and showed the same increase in melatonin output with age as the control ewes. These results indicate that the delayed puberty caused by melatonin implants is not due to decreased pituitary responsiveness to LHRH or to dramatic changes in basal LH or FSH secretion.
对青春期前的母羊羔用空的或填充褪黑素的植入物进行处理。植入物在出生时皮下植入，在10、19、28、36和45周龄时检测垂体对不同剂量促黄体生成素释放激素（LHRH）的反应性、促黄体生成素/促卵泡生成素（LH/FSH）的脉冲性以及催乳素和褪黑素的分泌。对照动物（N = 10）在发育过程中垂体对LHRH的反应性没有一致的改变。用褪黑素处理的母羊（N = 10）青春期开始延迟了4周（P < 0.03），但在任何发育阶段均未观察到褪黑素对LHRH注射引起的LH或FSH反应有影响。在对照和褪黑素处理的母羊羔中，在所有发育阶段，黑暗期间对LHRH注射的反应均低于白天。在处理组之间或发育过程中，未观察到LH或FSH脉冲性有一致的差异。然而，在褪黑素处理组中，催乳素浓度在青春期（秋季）时并未下降。褪黑素处理的母羊羔维持正常的褪黑素节律性分泌，其基础浓度较高，且与对照母羊一样，随着年龄增长褪黑素分泌量增加。这些结果表明，褪黑素植入物导致的青春期延迟并非由于垂体对LHRH的反应性降低或基础LH或FSH分泌的显著变化。
