Falcón J, Bolliet V, Ravault J P, Chesneau D, Ali M A, Collin J P
Laboratoire de Neurobiologie et Neuroendocrinologie Cellulaires, URA CNRS 1869, Université de Poitiers, France.
Neuroendocrinology. 1994 Nov;60(5):535-43. doi: 10.1159/000126792.
In the pineal organ of the pike (Esox lucius, teleost), the rhythmic production of melatonin by the photoreceptor cells is governed by a population of endogenous circadian oscillators, synchronized and entrained by the light/dark (L/D) cycle. Production of melatonin is inhibited by light and highly increased in the dark. In the present study, isolated and superfused pike pineals were exposed to a 24-hour temperature cycle of high (10 degrees C) or low (4 degrees C) amplitude, either under L/D, or under constant darkness. Under L/D, photoperiod is the dominant entraining stimulus for the melatonin secretion rhythm. It was high during the dark phase and low during the light phase, either under cold light/warm dark or under warm light/cold dark conditions. Under a warm light/cold dark cycle, the amplitude of the melatonin rhythm was reduced. In pineals cultured at 10 degrees C, a 20 degrees C temperature pulse potentiated or reduced the night-induced rise in melatonin production when applied, during the dark or during the preceding light phase, respectively. Under constant darkness, high- or low-amplitude temperature cycles could synchronize the rhythmic production of melatonin, which peaked with the high temperature. However, the shape of the oscillation could appear modified under warm subjective-L/cold subjective-D, depending on the experimental conditions. Finally, the rhythmic release of melatonin synchronized by a temperature cycle under constant darkness was no longer observed after removal of the external zeitgeber. The present study provides direct evidence that the pineal acts as a photothermotransducer.
在白斑狗鱼（硬骨鱼纲，梭子鱼）的松果体器官中，光感受器细胞褪黑素的节律性分泌受一群内源性昼夜节律振荡器控制，这些振荡器由光/暗（L/D）周期同步和调节。褪黑素的分泌受光抑制，在黑暗中则大量增加。在本研究中，分离并灌注的白斑狗鱼松果体在L/D条件下或持续黑暗条件下，暴露于高（10摄氏度）或低（4摄氏度）幅度的24小时温度循环中。在L/D条件下，光周期是褪黑素分泌节律的主要调节刺激。在冷光/暖暗或暖光/冷暗条件下，褪黑素在黑暗阶段分泌量高，在光照阶段分泌量低。在暖光/冷暗循环下，褪黑素节律的幅度减小。在10摄氏度培养的松果体中，当分别在黑暗或前一个光照阶段施加20摄氏度的温度脉冲时，该脉冲会增强或降低夜间诱导的褪黑素分泌增加。在持续黑暗条件下，高幅度或低幅度的温度循环可以使褪黑素的节律性分泌同步，其在高温时达到峰值。然而，根据实验条件，在暖主观白天/冷主观黑夜条件下，振荡的形状可能会出现改变。最后，在去除外部授时因子后，不再观察到在持续黑暗条件下由温度循环同步的褪黑素节律性释放。本研究提供了直接证据，证明松果体起到了光热换能器的作用。
