Melatonin (n-acetyl-5-methoxytryptamine) is a hormone produced by the pineal gland that has various functions. Classically known to control circadian rhythms and sleep-wake cycle, has recently been investigated for its antioxidant role, to preserve glycogen stores through modulation of lipid and carbohydrate metabolism during exercise and by the inhibition of transcriptional nuclear factor kappa B (NF-kB),concomitantly decreasing the signaling cascade of inflammation and oxidative stress. Most studies in this area, especially when they involve physical activity, is fragile in some intervenient parameters, such as the effects of circadian rhythm, control of exercise intensity and time of application of experimental procedures. Nevertheless, the literature reports unidirectional experiments, without taking into account the various properties of this hormone. Given this context, the objective of this project is to determine the ergogenic capacity of melatonin in exercise continued until exhaustion in lactate minimum intensity (LMi), in two times of day (higher and lower spontaneous activity), identifying the possible effects of this hormone in the circadian rhythm of rats spontaneous activity (CRRSA) and via IKK / NF-kB activity . To determine the CRRSA will be used a gravimetric system via strain gages, which consists in analyze the force responses on the rats cage, generated by muscular action, independent of kinematic activity of the animals, with 24 hours of monitoring and acquisition frequency of 1000Hz. To determine the effort intensity will be used the lactate minimum test in tethered swimming system. The force increments and monitoring of propulsion response will be captured in 1000Hz. The animals will be divided into 16 groups to be isolated from the following effects: melatonin administration, performance (exercise until exhaustion in LMi) and two times of day (higher and lower spontaneous activity). The animals will be euthanized 1 or 24 hours after the performance, in a CO2 chamber. The blood will be collected by cardiac puncture to determine the melatonin concentration. Muscle and liver tissues samples will be extracted to determination of glycogen concentration and IKK/NF-kB activity.
News published in Agência FAPESP Newsletter about the scholarship: