A capacidade intrínseca para o exercício físico está associada aos sistemas dopaminérgico e serotonérgico em áreas cerebrais

Abstract

The aim of the present study was to verify whether the intrinsic capacity for physical exercise is associated with the concentrations of serotonin, dopamine and its metabolites in the basal state and after a submaximal exercise. Male Wistar rats were submitted to three incremental exercise tests. Based on the maximal time of exercise (maxTE), a frequency histogram was developed and animals were divided in: low capacity (LC) with maxTE < averageTE in the histogram minus one standard deviation (SD) (LC: maxTE < 24.90 min), high capacity (HC) with maxTE > averageTE in the histogram plus one standard deviation (SD) (HC: maxTE > 57.10 min). The other animals were classified as standard capacity (SC) (SC: TE > 24.90 and < 57.10 min). The study consisted of two experimental protocols named: basal state and submaximal exercise (60% in the maximal velocity). The second experiment was constituted by two situations: rest and submaximal exercise, in which the thermoregulatory variables were registered. In all protocols of exercise, the time of exercise was higher in the HC compared to SC and LC, and it was lower in the LC compared to SC (p < 0.01). The exercise situation compared to the basal state resulted in the increase of ratio 5-HIAA/5-HT in the caudate-putamen (CPu), hippocampus and preoptic area (POA) of all animals (p < 0.01). In the accumbens (Acc), this response was observed only in the groups SC and HC (p < 0.01). After the exercise, the increase of serotonin turnover in the CPu and Acc was higher in the HC compared to the other experimental groups (p < 0.05). This result might be due to the highest ratio DOPAC/DA in the CPu (SC: 0.19 ± 0.02; LC: 0.20 ± 0.01; HC: 0.29 ± 0.03; p < 0.05). Positive correlations were found among TE and the basal concentrations of DA and DOPAC in the Acc, only in HC. Based on this result, it is possible to claim that HC has higher sensitivity of the pathway between the ventral tegmental area and Acc. In the LC group, in the basal state, there were identified higher values of 5-HIAA and serotonin turnover in the hippocampus, which may be associated with a low capacity to do exercise. HC finished the submaximal exercise with higher intraperitoneal temperature than SC and LC, which may be a consequence of the highest basal concentration of DA in the POA (SC: 7.72 ± 0.63; LC: 8.45 ± 0.66; HC: 11.50 ± 1.53 pg.g protein-1). During all exercise, the ratio 12 between the accumulated heat and work was lower in the HC group, which indicates a higher mechanical efficiency, and this ratio was higher in LC, which indicates a lower mechanical efficiency in these animals. This data suggests that the capacity to exercise is associated with dopaminergic and serotonergic variables in the basal state and after the physical exercise.