ABSTRACT
Melatonin is a small lipid - and water-soluble indoleamine (N-acetyl-5-methoxytryptamine) that can easily diffuse through cell membranes, and functions as an important signal molecule in unicellular organisms, plants, fungi, and also in animals and humans [1-5]. The primary site of its biosynthesis in humans is the pineal gland, but its production also occurs in the retina, gastrointestinal tract, skin, bone marrow cells, and lymphocytes [6-14]. Melatonin synthesis is closely related with sleep regulation (with nocturnal maximum) and other cyclic metabolic activities linked to biological clocks regulation, which enables order and temporal relationships in normal interactions of various bodily processes. Additionally, there is growing evidence that circulating hormones and other metabolic signals may modulate circadian oscillations via clock gene expression in some brain regions and peripheral structures, which in turn enable integration of circadian, hormonal, and metabolic information [15-18]. For example, melatonin modulates the rhythm of the clock gene Per1 in the pituitary gland, striatum, and adrenal cortex [19-22]. These inner clocks are also necessary for collecting information and creating temporal order of mental experience. Typical changes in temporal order of mental experience may occur during stress that presents a moment of cognitive con—ict associated with spatiotemporal disorganization and lack of order in mental experience including its temporal-episodic component. These disruptions of temporal integration likely play an important role in mental disorders and may cause dissociation of mental experience.
