Small Thomas W, Sharp Peter J, Bentley George E, Deviche Pierre
School of Life Sciences, Arizona State University, Tempe, AZ, USA.
J Biol Rhythms. 2008 Feb;23(1):69-80. doi: 10.1177/0748730407310790.
We tested the hypothesis that adult male rufous-winged sparrows, Aimophila carpalis, exhibit relative photorefractoriness. This condition results in partial loss of sensitivity to photoperiod as a reproductive stimulus after prolonged exposure to long photoperiods and is similar to the mammalian condition called photoperiodic memory. Captive birds were exposed either to 8 h of light/16 h of dark per day (8L) or to 16L for 11 weeks and were then exposed either to 8L, 13L, 14L, or 16L. Testicular diameter, plasma luteinizing hormone (LH), and plasma prolactin (PRL) were measured to assess reproductive system activity in response to photostimulation. In free-living birds, testicular diameter, plasma LH, and PRL were compared in birds caught in September in a year when birds were breeding and in a year when birds were not breeding to further evaluate the role of PRL in the termination of seasonal breeding. Testes completely developed after transfer from 8L to 14L or to 16L and partially developed after transfer from 8L to 13L. However, after 11 weeks of 16L exposure, transfer to 14L caused partial regression and transfer to 13L caused complete regression of the testes. Plasma LH increased in all birds that were transferred from 8L to a longer photoperiod. PRL showed a weak response to longer photoperiod treatment and was elevated in birds after chronic 16L exposure in comparison to birds exposed to chronic 8L. These data indicate that male rufous-winged sparrows lose sensitivity to photoperiod after long photoperiod exposure consistent with the relative photorefractoriness and photoperiodic memory models. Lower PRL in birds that developed testes on 13L and 14L compared to birds that regressed testes on 13L and 14L are consistent with the hypothesis that PRL regulates relative photorefractoriness. However, PRL does not appear to regulate interannual differences in the timing of testicular regression.
我们检验了成年雄性棕翅雀鹀（Aimophila carpalis）表现出相对不应性的假设。这种情况会导致在长时间暴露于长光照周期后，对作为繁殖刺激的光周期敏感性部分丧失，并且类似于哺乳动物的光周期记忆情况。将圈养鸟类每天暴露于8小时光照/16小时黑暗（8L）或16L环境中11周，然后再将它们暴露于8L、13L、14L或16L环境中。测量睾丸直径、血浆促黄体生成素（LH）和血浆催乳素（PRL），以评估生殖系统对光刺激的反应活性。在自由生活的鸟类中，比较了在鸟类繁殖年份的9月捕获的鸟类和非繁殖年份的9月捕获的鸟类的睾丸直径、血浆LH和PRL，以进一步评估PRL在季节性繁殖终止中的作用。从8L转移到14L或16L后，睾丸完全发育，从8L转移到13L后，睾丸部分发育。然而，在暴露于16L环境11周后，转移到14L会导致睾丸部分退化，转移到13L会导致睾丸完全退化。从8L转移到更长光照周期的所有鸟类，其血浆LH均增加。PRL对更长光照周期处理的反应较弱，与长期暴露于8L的鸟类相比，长期暴露于16L的鸟类的PRL升高。这些数据表明，雄性棕翅雀鹀在长时间光照周期暴露后对光周期失去敏感性，这与相对不应性和光周期记忆模型一致。与在13L和14L环境中睾丸退化的鸟类相比，在13L和14L环境中睾丸发育良好的鸟类的PRL较低，这与PRL调节相对不应性的假设一致。然而，PRL似乎并不调节睾丸退化时间的年际差异。
