Effects of moderate and intensive training on the hypothalamo–pituitary–adrenal axis in rats

Abstract

The influence of the two distinct training programmes, moderate (M) and intensive (I), on hypothalamo-pituitary-adrenal (HPA) axis was investigated, in rats. Changes in plasma concentrations of adrenocorticotropin hormone (ACTH) and corticosterone were followed in response to (i) a 60-min acute running session performed on 2nd, 4th and 6th of the seven training weeks (ii) an acute restraint stress of 40 min applied after the final training programme. After 2nd, 4th and 6th week of the two training programmes, a 60-min running resulted in an enhanced secretion of ACTH and corticosterone, compared with both the baseline values (i.e. before running) and to the sedentary (S) group. However, on 4th and 6th weeks compared with 2nd week, ACTH and corticosterone remained elevated in intensive group when they are significantly reduced in moderate group. We could suggest that a moderate training resulted in an adapted hormonal response whereas a deadapted process occurred for the intensive programme. The day after the last training session, basal ACTH, corticosterone and corticosteroid-binding globulin (CBG) capacity were not affected by training. Hypothalamic corticotropin-releasing factor tissue-content (CRF) was increased significantly in the two trained groups. When compared with the sedentary group, the body weight of the rats in the two trained groups was significantly decreased with a total adrenal mass increasing but only in intensive group. The surimposed restraint stress resulted in significant increases in plasma ACTH and corticosterone both in trained and in sedentary animals. This result suggests that the adapted HPA axis response induced by both a moderate and intensive training do not prevent against the effects of a novel stress such as restraint stress.

Influência dos exercícios físicos de baixa e alta intensidade sobre o limiar de hipernocicepção e outros parâmetros em ratos

“…These results corroborate the literature with trained rats on treadmill under high intensity protocols, which reduce the food intake with consequent weight loss (31)(32)(33)(34)(35)(36)(37)(38)(39)(40)(41)(42)(43)(44)(45)(46)(47)(48) . As mentioned before and reinforcing such idea, physical exercises represent a type of stress and promote CRH release by the hypothalamus due to the dependence of the stressor agent intensity.…”

“…Actually, Oliveira et al (54) reported that the primary function of the kidneys is to regulate the volume and composition of the extra cellular liquid, and hence, these alterations that occur during the performance of physical exercises may generate hemodynamic changes and changes in the sodium and water excretion. The findings of this study concerning the kidneys weight of the trained animals do not confirm the findings of the literature (45)(46)(47)(48)(49)(50)(51)(52)(53)(54)(55) , showing decrease in this organ's weight, maybe by the decrease of the number of glomerulus caused by the hypoxia conditions imposed by the exercises. One of the possible causes of this results divergence may be the fact that the research was performed with rats too young for the physical training, differently from the age of the rats from this study.…”

“…Therefore, it is possible that a rats' body adaptation to the high intensity exercises would be more difficult in comparison to low intensity ones. According to this hypothesis, the results of other research in rats, are conclusive in the demonstration that exercises promote hypertrophy of the adrenal glands (31)(32)(33)(34)(35)(36)(37)(38)(39)(40)(41)(42)(43)(44)(45) and that the physical training intensity influences the intensity-dependent response of the hypothalamus-hypophysis-adrenal axis activation (46) . Therefore, the results obtained here suggest the participation of these hormones in the antinociceptor effects, even if the rats have been evaluated after 16 hours of the end of physical training.…”

Voluntary wheel running initially increases adrenal sensitivity to adrenocorticotrophic hormone, which is attenuated with long-term training

“…The effects of regular exercise on diurnal GC levels and adrenal sensitivity to ACTH secretion are unclear. Previously, a number of rodent studies investigating the effects of training on the HPA axis have employed forced exercise paradigms for their method of training (1,25,27,36). Such studies have produced findings that are similar to those of investigations employing chronic stress (e.g., repeated restraint stress) as an activator of the axis (17,32), making it difficult to delineate the effects of perceived stress from the exercise itself.…”

Metabolic and behavioral responses to high-fat feeding in mice selectively bred for high wheel-running activity

“…For example, forced treadmill running, water immersion and so on. 10,11 are perceived as psychological stress, 12 which may complicate interpretation of results. A preferred method is the use of running wheels in which rodents can run voluntarily.…”