Prolonged Melatonin Synthesis During Long Nights: Mechanisms

松果体是一个连接眼睛的小器官，位于大脑中心附近，产生一种激素，为身体提供重要的时间信息。松果体只有在天黑的时候才会释放褪黑激素到血液中，从而完成这种计时功能。正因为如此，白天血液中的褪黑素水平较低，而晚上则较高。由于褪黑激素的昼夜变化，身体的每个器官都被赋予了信息，即使与眼睛没有联系，关于它是亮还是暗。当白昼长度（当然还有黑夜长度）发生变化时，比如在一年中的不同季节，松果体发出的褪黑激素信息也会发生相应的变化。松果体能够在冬夜长时间释放高水平褪黑素的生物学机制尚不清楚。本研究的目的是定义这是如何实现的。问题是，是大脑“命令”松果体需要多长时间才能产生褪黑激素，还是松果体决定自己的命运并调节褪黑激素释放的持续时间。概述的研究将检验这些问题。收集到的信息将适用于许多重要的生物学问题，例如动物的季节性繁殖，羊毛生长和产奶量的季节性变化，工作效率的日常变化，理解“时差”和轮班工人适应新时间表的能力，以及理解“冬季抑郁症”等情况。

The pineal gland, a small organ connected to the eyes and located near the center of the brain, produces a hormone that provides important timing information to the body. The pineal gland accomplishes this timing function by releasing the hormone melatonin into the blood only during darkness. Because of this, daytime levels of melatonin in the blood are low while they are high at night. Due to these day/night changes in melatonin, every organ in the body is given information, even though not connected to the eyes, as to whether it is light or dark. When day length (and of course night length change), such as during the various seasons of the year, the melatonin message from the pineal gland also changes accordingly. The biological mechanisms whereby the pineal gland is able to release high melatonin levels for longer periods during winter nights are unknown. The purpose of this research is to define how this is accomplished. The problem is, does the brain "dictate" to the pineal gland how long it must produce melatonin or does the pineal gland determine its own fate and regulate the duration of melatonin release. The studies outlined will examine these questions. The information garnered will be applicable to a number of important biological problems, e.g. seasonal reproduction in animals, seasonal variation in wool growth and milk production, daily variations in work efficiency, understanding "jet lag" and the ability of shift workers to adapt to new schedules, as well as understanding conditions such as "winter depression".