Abstract：
Temporal signals such as light and temperature cycles profoundly modulate animal physiology and behaviour. Via endogenous timing mechanisms which are regulated by these signals, organisms can anticipate cyclic environmental changes and thereby enhance their fitness. The pineal gland in fish, through the secretion of melatonin, appears to play a critical role in the circadian system, most likely acting as an element of the circadian clock system. An important output of this circadian clock is the locomotor activity circadian rhythm which is adapted to the photoperiod and thus determines whether animals are diurnal or nocturnal. By using a genetically modified zebrafish strain known as Tg (Xla.Eef1a1:Cau.asip1)iim04, which expresses a higher level of the agouti signalling protein 1 (Asip1), an endogenous antagonist of the melanocortin system, we observed a complete disruption of locomotor activity patterns, which correlates with the ablation of the melatonin daily rhythm. Consistent with this, in vitro experiments also demonstrated that Asip1 inhibits melatonin secretion from the zebrafish pineal gland, most likely through the melanocortin receptors expressed in this gland. Asip1 overexpression also disrupted the expression of core clock genes, including per1a and clock1a, thus blunting circadian oscillation. Collectively, these results implicate the melanocortin system as playing an important role in modulating pineal physiology and, therefore, circadian organisation in zebrafish.
摘要：
诸如光和温度周期的时间信号深刻地调节动物生理学和行为。通过这些信号调节的内源性时序机制，生物体可以预测周期性的环境变化，从而增强其适应性。鱼的松果体,通过分泌褪黑激素，似乎在昼夜节律系统中起着至关重要的作用，最有可能充当昼夜节律时钟系统的元素。该昼夜节律时钟的重要输出是适应光周期的运动活动昼夜节律，因此确定动物是昼夜还是夜间活动。通过使用称为Tg（Xla。Eef1a1：考尔。asip1）iim04，它表达更高水平的agouti信号蛋白1（Asip1），黑皮质素系统的内源性拮抗剂，我们观察到运动活动模式完全中断，这与褪黑素日常节律的消融有关。与此一致，体外实验还表明，Asip1抑制斑马鱼松果体分泌褪黑激素，很可能是通过在这个腺体中表达的黑皮质素受体。Asip1过表达也破坏了核心时钟基因的表达，包括per1a和clock1a，从而使昼夜节律振荡变得迟钝。总的来说，这些结果表明黑皮质素系统在调节松果体生理中起着重要作用，因此,斑马鱼的昼夜节律组织。
