title: The improvement of exercise performance by physical training is related to increased hypothalamic neuronal activation.
abstract: The effects of physical training on hypothalamic activation after exercise and their relationship with heat dissipation were investigated. Following 8 weeks of physical training, trained (TR, n = 9) and untrained (UN, n = 8) Wistar rats were submitted to a regimen of incremental running until fatigue while body and tail temperatures were recorded. After exercise, hypothalamic c-Fos immunohistochemistry analysis was performed. The workload, body-heating rate, heat storage and body temperature threshold for cutaneous vasodilation were calculated. Physical training increased the number of c-Fos immunoreactive neurons in the paraventricular, medial preoptic and median preoptic nucleus by 112%, 90% and 65% (P < 0.01) after exercise, respectively. In these hypothalamic regions, increased neuronal activation was directly associated with the increased workload performed by TR animals (P < 0.01). Moreover, a reduction of 0.6°C in the body temperature threshold for cutaneous vasodilation was shown by TR animals (P < 0.01). This reduction was possibly responsible for the lower body-heating rate (0.019 ± 0.002°C/min, TR vs 0.030 ± 0.005°C/min, UN, P < 0.05) and the decreased ratio between heat storage and the workload performed by TR animals (18.18 ± 1.65 cal/kg, TR vs 31.38 ± 5.35 cal/kg, UN, P < 0.05). The data indicate that physical training enhances hypothalamic neuronal activation during exercise. This enhancement is the central adaptation relating to better physical performance, characterized by a lower ratio of heat stored to workload performed, due to improved heat dissipation.
authors.affiliation: Department of Physiology and Biophysics, Institute of Biological Sciences, Federal University of Minas Gerais, Belo Horizonte, Minas Gerais, Brazil.
authors.forename: Henrique P
authors.initials: HP
authors.lastname: Santiago
authors.affiliation: Department of Physiology, Institute of Biological Sciences, Federal University of Juiz de Fora, Juiz de Fora, Minas Gerais, Brazil.
authors.forename: Laura H R
authors.initials: LH
authors.lastname: Leite
authors.affiliation: Department of Physiology and Biophysics, Institute of Biological Sciences, Federal University of Minas Gerais, Belo Horizonte, Minas Gerais, Brazil.
authors.forename: Paulo Marcelo A
authors.initials: PM
authors.lastname: Lima
authors.affiliation: Department of Physiology and Biophysics, Institute of Biological Sciences, Federal University of Minas Gerais, Belo Horizonte, Minas Gerais, Brazil.
authors.forename: Gisele V
authors.initials: GV
authors.lastname: Rodovalho
authors.affiliation: Department of Physiology and Biophysics, Institute of Biological Sciences, Federal University of Minas Gerais, Belo Horizonte, Minas Gerais, Brazil.
authors.forename: Raphael E
authors.initials: RE
authors.lastname: Szawka
authors.affiliation: Department of Physiology and Biophysics, Institute of Biological Sciences, Federal University of Minas Gerais, Belo Horizonte, Minas Gerais, Brazil.
authors.forename: Cândido C
authors.initials: CC
authors.lastname: Coimbra
mesh_terms: D000818:Animals; D001833:Body Temperature Regulation; D005786:Gene Expression Regulation; D006358:Hot Temperature; D007031:Hypothalamus / Q000166:cytology* / Q000502:physiology; D008297:Male; D009474:Neurons / Q000166:cytology*; D010805:Physical Conditioning, Animal / Q000502:physiology; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar
chemical_list: D016760:Proto-Oncogene Proteins c-fos
keywords: c-Fos; fatigue; paraventricular nucleus; preoptic area; thermoregulation