The Profile of Exercise‐induced Neuronal Activation in Autonomic Control Nuclei Changes According to Thermoregulatory Phase

Abstract

The purpose of this study was to examine whether the neuronal recruitment induced by exercise in autonomic nuclei is dependent of thermoregulatory phase and/or physical performance. Rats that were subjected to submaximal running exercise stopped in 3 different times: REST (control group), NADIR (the minimum heat dissipation phase), 20MIN (the stabilization phase of both body temperature ‐ Tb ‐ and tail skin temperature ‐ Tsk), and FATIGUE (Tb and Tsk reach their highest values​).The brains were removed and processed for determination of c‐Fos expression in the medial, median, and ventromedial preoptic areas (mPOA, mnPOA, and vmPOA, respectively), and paraventricular and supraoptic nucleus of hypothalamus (PVN and SON, respectively). Physical exercise induced an increase of c‐Fos expression in all brain areas. The c‐Fos expression in the vmPOA was similar for all exercising groups, while for mPOA, mnPOA, and PVN, it was gradually increased as the exercise and hyperthermic response are prolonged. Only after 20 min of exercise an increase in SON c‐Fos expression was verified. The neuronal recruitment within the mPOA, mnPOA, PVN, and SON was directly correlated to both physical performance and heat storage. The thermoregulatory brain areas are recruited even at small Tb changes, while the SON is recruited only when Tb reaches its higher values, possibly inducing changes on fluid balance. The recruitment rate in these areas is also influenced by duration of stress stimulus, either by increasing running time, as the prolonged hyperthermic response arising of exercise. Cnpq, Capes, and Fapemig.