Rhythmic Control and Physiological Functional Significance of Melatonin Production in Circadian Rhythm

Abstract

Circadian rhythm is controlled by hormonal oscillations governing the physiology of all living organisms. In mammals, the main function of the pineal gland is to transform the circadian rhythm generated in the hypothalamic suprachiasmatic nucleus into rhythmic signals of circulating melatonin characterized by a largely nocturnal increase that closely reflects the duration of night time. The pineal gland has lost direct photosensitivity, but responds to light via multi-synaptic pathways that include a subset of retinal ganglion cells. Rhythmic control is achieved through a tight coupling between environmental lighting and arylalkylamine-N-acetyltransferase (AANAT) expression, which is the rhythmcontrolling enzyme in melatonin synthesis. Previous studies on the nocturnal expression of AANAT protein have described transcriptional, post-transcriptional, and post-translational regulatory mechanisms. Molecular mechanisms for dependent AANAT expression provide novel aspects for melatonin's circadian rhythmicity. Extensive animal research has linked pineal melatonin for the expression of seasonal rhythmicity in many mammalian species to the modulation of circadian rhythms and to sleep regulation. It has value in treating various circadian rhythm disorders, such as jet lag or shift-work sleep disorders. Melatonin, also, in a broad range of effects with a significant regulation influences many of the body's physiological functions. In addition, this hormone is known to influence reproductive, cardiovascular, and immunological regulation as well as psychiatric disorders.

The Effects of Milking Time on Melatonin and Cortisol Concentrations in Raw Milk and Milk Powder during the Summer and Winter Solstice

“…이 두 효소는 빛에 의해 활성이 저해되므 로 체내 멜라토닌 농도는 빛의 유무에 따라 영향을 받는다. 즉, 멜라토닌의 합성과 분비는 암기에 촉진되고, 명기에 억제 된다(Wurtman et al, 1963;Kim et al, 2013). 멜라토닌의 대 표적인 생리적 기능으로는 신체를 이완시키고, 수면을 유도 하는 것이다.…”