Pinealectomy can cause a disturbance in emotional status and circadian rhythms of the endocrine and metabolic functions in the body. Endurance training is considered a part of the complex therapy of dysfunctions driven by changes in circadian dynamics of many physiological indicators. In the present study, we aimed to study the effect of endurance training on depressive behavior induced by pinealectomy in rat. We tested the hypothesis that endurance training can have a beneficial impact on depressive behavior induced by pinealectomy in rat via correction of desynchronized circadian rhythms of corticosterone secretion in plasma and brain-derived neurothrophic factor (BDNF) in the hippocampus. The continuous exercise program attenuated depressive responses characterized by the disrupted diurnal rhythm of home-cage motor activity, anhedonia in the sucrose preference test, decreased grooming in the splash test, and despair-like behavior in the forced swimming test of rats with pinealectomy to values resembling those of sham-treated controls. Parallel to the observed positive effect on the emotional status, exercise training diminished total plasma corticosterone levels and corrected its flattened pattern. While the melatonin deficiency did not affect the fluctuations of the BDNF levels, the exercise program induced a considerable and time-dependent increase in its level. These findings suggest that the antidepressant-like effect of endurance training might be mediated via correction of the disturbed circadian rhythm of corticosterone release and enhancement of hippocampal BDNF levels in rats with pinealectomy. Therefore, this alternative mode might have a potential therapeutic application in a subpopulation of people characterized by a melatonin deficiency.
Keywords: BDNF; Circadian rhythms; Depression; Endurance training; Pinealectomy; orticosterone.
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