Prolonged Melatonin Synthesis During Long Nights: Mechanisms

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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".