Lumineau S, Guyomarc'h C, Boswell T, Richard J P, Leray D
U.M.R. 6552, Ethologie Evolution Ecologie, Université de Rennes 1-C.N.R.S., Rennes, France.
J Biol Rhythms. 1998 Aug;13(4):278-87. doi: 10.1177/074873098129000110.
Studies in vertebrates have shown that hormones can influence circadian rhythms of behavior. We investigated whether testosterone could induce rhythmicity in arrhythmic Japanese quail, kept in DD. The animals used were 3 1/2-week-old castrated males from a line of quail selected for the lack of the circadian rhythm of feeding activity. After 3 weeks in DD, 8 birds were implanted with an empty implant and 16 others with a testosterone implant. Two weeks later, the operation was repeated. After implantation, we noticed that 15 out of 16 testosterone-treated birds showed a circadian rhythm of feeding activity, in contrast to the control birds, which remained arrhythmic. The clarity of this rhythm increased significantly after each implantation. A positive correlation was found between the indexes of clarity of the rhythm (autocorrelation coefficient ratio and area of the peak of spectrum) and the plasma testosterone level. The period of the induced free-running rhythm was identical to the specific value of the endogenous circadian rhythm in immature quail. The circadian period showed a significant lengthening with the second implantation. This lengthening looks like the variation previously observed in maturing rhythmic or implanted quail. So, it would appear that testosterone can act on rhythmicity on at least two levels: by inducing the circadian rhythm and increasing its clarity and by modulating its period. To explain these results, several hypotheses can be considered. First, the observed arrhythmy may be the consequence of an internal desynchronization of oscillators, responsible for generating the circadian rhythm of feeding activity, and testosterone could play a role in the coupling of these oscillators. Alternatively, we suggest that testosterone could act on the transcription of genes implicated in the control of the rhythmicity or may regulate by rapid signals the cellular rhythmic activity. The possible functional values of the enhancing of circadian rhythmicity by testosterone at different stages of the bird's life were discussed.
对脊椎动物的研究表明，激素可影响行为的昼夜节律。我们研究了睾酮是否能在持续黑暗（DD）环境中饲养的无节律日本鹌鹑中诱导节律性。所用动物为3.5周龄、来自因缺乏进食活动昼夜节律而被挑选出的鹌鹑品系的阉割雄性鹌鹑。在DD环境中饲养3周后，8只鸟植入空植入物，另外16只植入睾酮植入物。两周后，重复该手术。植入后，我们注意到16只接受睾酮处理的鸟中有15只表现出进食活动的昼夜节律，而对照鸟仍无节律。每次植入后，这种节律的清晰度显著增加。发现节律清晰度指标（自相关系数比和频谱峰值面积）与血浆睾酮水平之间存在正相关。诱导的自由运行节律的周期与未成熟鹌鹑内源性昼夜节律的特定值相同。第二次植入后，昼夜周期显著延长。这种延长类似于先前在成熟的有节律或植入的鹌鹑中观察到的变化。因此，似乎睾酮可以至少在两个层面上作用于节律性：通过诱导昼夜节律并提高其清晰度，以及通过调节其周期。为了解释这些结果，可以考虑几种假设。首先，观察到的无节律可能是负责产生进食活动昼夜节律的振荡器内部去同步化的结果，而睾酮可能在这些振荡器的耦合中起作用。或者，我们认为睾酮可能作用于与节律性控制相关的基因的转录，或者可能通过快速信号调节细胞的节律活动。讨论了睾酮在鸟类生命不同阶段增强昼夜节律性的可能功能价值。
