Sleep modulation melatonin

The permissive serotonin hypothesis proposes that serotonin (5-hydroxytryptamine or 5-HT) plays a critical role in modulating brain activity (e.g., stabilization of the catecholamine system and inhibition of dopamine [DA] release), and is low in both mania and depression. L-tryptophan or 5-HT deficiency and changes in the light-dark cycle may result in reduced melatonin secretion from the pineal gland that disrupts the sleep-wake cycle, alters circadian rhythms, and causes seasonal affective changes. ... 

Indole is perhaps the most visible heterocycle in all of chemistry. Since Adolf von Baeyer proposed the structure of indole as a heteroaromatic compound 140 years ago, indole has embodied a myriad of natural products, pharmaceutical agents, and a growing list of polymers. In the human body, serotonin modulates 5-hydroxytryptamine (5-HT), a monoamine neurotransmitter primarily found in the gastrointestinal (GI) tract and central nervous system (CNS), and modulates vasoconstriction and many brain activities. Melatonin regulates circadian rhythms, most noticeably, sleep. Tryptamine is closely related to melatonin and the amino acid tryptophan. 

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