Delgadillo J A, Chemineau P
INRA Physiologie de la Reproduction, Nouzilly, Monnaie, France.
J Reprod Fertil. 1992 Jan;94(1):45-55. doi: 10.1530/jrf.0.0940045.
This study was performed to determine whether rapid alternation between long and short days abolished seasonal variations in the activity of the hypothalamo-pituitary-testis axis observed normally in Alpine and Saanen male goats during the year. Three groups of 6 males were used: group 1 remained in open sheds under the natural annual change in daylength from 16 h of light (long day) to 8 h of light (short day). Group 2 was exposed to 1 month of long days alternated with 1 month of short days; and group 3 to 2 months of long days alternated with 2 months of short days. In group 1, blood samples were taken in December, February and June; in groups 2 and 3, samples were obtained once during short and long days for the melatonin assay. For luteinizing hormone and testosterone determinations monthly samples from group 1 were obtained from September to August while, in groups 2 and 3, blood samples were taken on 4 occasions during long and short days. Weekly blood samples were taken from all groups during the whole of the experiment to measure prolactin and testosterone concentrations. Melatonin profiles indicated that secretion by the pineal gland of male goats from the treated groups adapted to rapid changes in daylength: duration of nocturnal secretion was close to that of the dark period. Treated goats were also able to transduce this signal adequately and always responded to long days by increasing their prolactin concentration (mean +/- s.e.m.; group 2: 62.4 +/- 6.8 ng/ml; group 3: 102.3 +/- 15.7 ng/ml) and to short days with a decrease in prolactin concentrations (35.0 +/- 3.6 and 46.1 +/- 9.5 ng/ml, respectively). In the treated groups, luteinizing hormone pulse frequency varied with day length. In group 2, it was higher in long days (1.1 +/- 0.3 pulses in 8 hours) than in short days (0.7 +/- 0.3) while, in group 3, this frequency was higher in short days (1.9 +/- 0.3) than in long days (0.5 +/- 0.2). Testosterone secretion also varied with daylength; in group 2, the testosterone concentrations were maximum during long days (5.8 +/- 1.4 ng/ml) while in group 3 the maximum testosterone concentrations occurred during short days (6.4 +/- 1.2 ng/ml). These results lead to the conclusion that rapid alternation of long and short days either attenuated (group 3) or prevented (group 2) seasonal changes in the activity of the hypothalamo-pituitary axis.(ABSTRACT TRUNCATED AT 400 WORDS)
本研究旨在确定长短日照的快速交替是否能消除阿尔卑斯山羊和萨能山羊雄性在一年中正常观察到的下丘脑 - 垂体 - 睾丸轴活动的季节性变化。使用了三组，每组6只雄性山羊：第1组山羊饲养在开放式羊舍中，接受自然年度日照长度变化，从16小时光照（长日照）到8小时光照（短日照）。第2组山羊经历1个月长日照与1个月短日照的交替；第3组山羊经历2个月长日照与2个月短日照的交替。第1组在12月、2月和6月采集血样；第2组和第3组在短日照和长日照期间各采集一次血样用于褪黑素检测。对于促黄体生成素和睾酮的测定，第1组从9月至8月每月采集血样，而第2组和第3组在长日照和短日照期间各采集4次血样。在整个实验过程中，每周从所有组采集血样以测量催乳素和睾酮浓度。褪黑素谱表明，处理组雄性山羊松果体的分泌适应了日照长度的快速变化：夜间分泌持续时间接近黑暗期。处理过的山羊也能够充分传导这一信号，并且总是在长日照时通过增加催乳素浓度做出反应（平均值±标准误；第2组：62.4±6.8 ng/ml；第3组：102.3±15.7 ng/ml），在短日照时催乳素浓度降低（分别为35.0±3.6和46.1±9.5 ng/ml）。在处理组中，促黄体生成素脉冲频率随日照长度而变化。在第2组中，长日照时（8小时内1.1±0.3次脉冲）高于短日照时（0.7±0.3次），而在第3组中，短日照时（1.9±0.3次）高于长日照时（0.5±0.2次）。睾酮分泌也随日照长度而变化；在第2组中，长日照时睾酮浓度最高（5.8±1.4 ng/ml），而在第3组中，短日照时睾酮浓度最高（6.4±1.2 ng/ml）。这些结果得出结论，长短日照快速交替要么减弱了（第3组）要么阻止了（第2组）下丘脑 - 垂体轴活动的季节性变化。（摘要截选至400字）
