Os efeitos do treinamento físico aeróbio sobre a síntese de melatonina pineal em ratos.

Abstract

Silva-Junior JS. Effects of the aerobic exercise training on pineal melatonin synthesis in rats. [Masters thesis (Human Physiology)]. Sao Paulo: Instituto de Ciencias Biomedicas, Universidade de Sao Paulo; 2015. The pineal gland is responsible for melatonin synthesis and secretion, which in turn participates in the temporal organization of biological rhythms acting as a mediator between the light / dark environmental and regulatory physiological processes including modulation of sleep / activity and sleep / wake cycles, among others. Melatonin synthesis is controlled by the nocturnal release of norepinephrine by the axons of sympathetic postganglionic neurons innervating the pineal gland. Its production can be modulated by yet other regions of the central nervous system and various constituents of the peptidergic system. The exercise promotes a significant increase in the activity of peripheral sympathetic neurons and consequently the release of noradrenaline. In this way, the exercise could modulate the release of noradrenaline by the sympathetic innervation of the pineal gland, and thus modulate melatonin synthesis. Nonetheless, melatonin synthesis modulation by exercise is still controversial. On the other hand, both streptozotocin-induced diabetes and the physiological aging process significantly decrease the pineal synthesis and plasma melatonin concentration in rats. The aim of this study was to evaluate the effects of aerobic exercise training on pineal melatonin synthesis in rats under various conditions (healthy adults rats, aged ones and untreated type 1 diabetic animals). Wistar rats were randomly assigned to the following groups, 1) 8-week training period: Sedentary Adult (AS); Trained Adult (AT); Sedentary Aged (IS); Trained Aged (IT), and 2) 5-week training period: Sedentary Control (CS); Trained Control (CT); Sedentary Diabetic (DS); Trained Diabetic (DT). After euthanasia at ZT18, the pineal glands were removed for evaluation of the melatonin content, AANAT enzyme activity and gene expression of the enzymes involved in melatonin synthesis, as well as the adrenergic receptors (β1, α1). Trained adult animals showed no difference in melatonin production throughout the scotophase and the diabetic animals showed no difference in the AANAT activity at ZTs 18 and 21. Aged animals showed an increase in AANAT enzyme activity and increased gene expression of beta adrenergic receptor at ZT 18. In conclusion, the aerobic exercise does not alter pineal melatonin synthesis in adult animals and in diabetic ones, but possibly increases it in trained aged animals by increasing the β1 adrenergic receptor expression and the AANAT activity, the rate limiting enzyme in melatonin synthesis.