Centro de Investigación en Reproducción Caprina, Universidad Autónoma Agraria Antonio Narro, Periférico Raúl López Sánchez y Carretera a Santa Fe, C.P. 27054 Torreón, Coahuila, Mexico.
PRC, INRA, CNRS, Université de Tours, IFCE, Agreenium, Nouzilly, France.
Domest Anim Endocrinol. 2017 Jul;60:42-49. doi: 10.1016/j.domaniend.2017.03.004. Epub 2017 Mar 31.
We showed previously that the permanent presence of bucks rendered sexually active by photoperiodic treatments, thereafter called photostimulated bucks, prevents the occurrence of seasonal anovulation; also, the introduction of these sexually active bucks induces ovulations during seasonal anestrus. Here, we studied the response of ovariectomized goats bearing 12-mm subcutaneous implants filled or not with estradiol to sexually active males to determine (1) whether the permanent presence of such bucks prevents the decrease of LH despite the presence of a negative feedback by estradiol mimicking that of seasonal anestrus (experiment 1) and (2) whether the introduction of photostimulated bucks increases the plasma LH concentrations in spite of this negative feedback (experiment 2). In experiment 1, one group of goats remained in contact with sexually active bucks, whereas the other group remained in contact with control bucks. Plasma LH concentrations were high and did not differ with time or between groups of females from November to February (P > 0.05), when both types of bucks were sexually active. Afterward, in goats in contact with control and sexually inactive bucks, LH concentrations decreased from March (P ≤ 0.01) and remained low until May, whereas LH levels remained high from March to May in goats in contact with the photostimulated bucks (P > 0.05). In experiment 2, 2 groups of females bearing empty subcutaneous implants, and 2 groups of goats bearing subcutaneous implants filled with estradiol, were exposed to control or photostimulated bucks. Plasma LH concentrations did not increase in goats bearing empty implants, when exposed to control or photostimulated bucks (from 2.01 ± 0.26 to 1.98 ± 0.31 ng/mL, and from 2.45 ± 0.29 to 2.42 ± 0.21 ng/mL respectively; P > 0.05). In contrast, plasma LH concentrations increased from 0.97 ± 0.41 to 2.80 ± 0.62 ng/mL in goats exposed to the photostimulated bucks and bearing estradiol implants (P < 0.05). Thus, the permanent presence of sexually active bucks prevented the decrease of plasma LH concentration in OVX + E2 goats during the seasonal anestrus, and the introduction of the photostimulated bucks increased the plasma LH concentrations in OVX + E2 goats during the seasonal anestrus. Therefore, we conclude that in both cases, the photostimulated bucks are able to reduce or counterbalance the seasonal negative feedback of estradiol on LH secretion.
我们之前曾表明，通过光周期处理使雄性保持性活跃的公鹿（此后称为光刺激公鹿）可防止季节性乏情时发生不排卵；此外，引入这些性活跃的公鹿可在季节性乏情期间诱导排卵。在这里，我们研究了卵巢切除术山羊对性活跃公鹿的反应，以确定（1）永久性接触这些公鹿是否可以防止 LH 水平下降，尽管存在模拟季节性乏情的雌二醇负反馈（实验 1），以及（2）引入光刺激公鹿是否可以增加血浆 LH 浓度，尽管存在这种负反馈（实验 2）。在实验 1 中，一组山羊与性活跃的公鹿保持接触，而另一组则与对照公鹿保持接触。从 11 月到 2 月（P>0.05），当两种公鹿都具有性活跃性时，血浆 LH 浓度很高，且不受时间或雌性动物组别的影响。此后，在与对照和非活跃公鹿接触的山羊中，LH 浓度从 3 月开始下降（P≤0.01），并一直保持较低水平，直到 5 月，而在与光刺激公鹿接触的山羊中，LH 水平从 3 月到 5 月保持较高水平（P>0.05）。在实验 2 中，两组携带空皮下植入物的雌性和两组携带充满雌二醇的皮下植入物的山羊，分别暴露于对照或光刺激公鹿。当暴露于对照或光刺激公鹿时，携带空植入物的山羊的血浆 LH 浓度并未增加（分别从 2.01±0.26 至 1.98±0.31ng/mL 和从 2.45±0.29 至 2.42±0.21ng/mL；P>0.05）。相比之下，暴露于光刺激公鹿且携带雌二醇植入物的山羊的血浆 LH 浓度从 0.97±0.41 增加到 2.80±0.62ng/mL（P<0.05）。因此，永久性接触性活跃的公鹿可防止卵巢切除+ E2 山羊在季节性乏情期间 LH 浓度的下降，并且引入光刺激公鹿可增加卵巢切除+ E2 山羊在季节性乏情期间的血浆 LH 浓度。因此，我们得出结论，在这两种情况下，光刺激公鹿都能够减少或抵消雌二醇对 LH 分泌的季节性负反馈。
