title: Increased brain L-arginine availability facilitates cutaneous heat loss induced by running exercise.
abstract: The effects of increased brain availability of L-arginine (L-arg), a precursor for nitric oxide synthesis, on core body temperature (Tcore ) and cutaneous heat loss were evaluated in running rats. One week prior to the experiments, adult male Wistar rats received the following implants: a chronic guide cannula in the lateral cerebral ventricle and a temperature sensor in the abdominal cavity. On the day of the experiments, the rats were assigned to receive a 2-μL intracerebroventricular injection of either NaCl (0.15 mol/L) or L-arg solution (0.825, 1.65 or 3.30 mol/L); Tcore and tail skin temperature were measured while the rats ran at a speed of 18 m/min until they were fatigued. L-arginine induced a dose-dependent reduction in the threshold Tcore required for cutaneous heat loss (38.09 ± 0.20°C for 3.30-mol/L L-arg vs 38.61 ± 0.10°C for saline; P < 0.05), which attenuated the exercise-induced hyperthermia. Although the rats treated with L-arg presented a lower Tcore at the end of exercise (~0.7°C lower after treatment with the highest dose), no changes in the time to fatigue were observed relative to the control trial. These results suggest that brain L-arg controls heat loss during exercise, most likely by modulating the sympathetic vasoconstrictor tonus to skin vessels. Furthermore, despite facilitating cutaneous heat loss mechanisms, increased brain L-arg availability did not enhance physical performance.
authors.affiliation: Department of Physiology and Biophysics, Institute of Biological Sciences, Federal University of Minas Gerais, Belo Horizonte, Brazil.|Exercise Physiology Laboratory, School of Physical Education, Physiotherapy and Occupational Therapy, Federal University of Minas Gerais, Belo Horizonte, Brazil.
authors.forename: Samuel Penna
authors.initials: SP
authors.lastname: Wanner
authors.affiliation: Department of Physiology and Biophysics, Institute of Biological Sciences, Federal University of Minas Gerais, Belo Horizonte, Brazil.|Department of Physiology, Institute of Biological Sciences, Federal University of Juiz de Fora, Juiz de Fora, Brazil.
authors.forename: Laura Hora Rios
authors.initials: LH
authors.lastname: Leite
authors.affiliation: Department of Physiology and Biophysics, Institute of Biological Sciences, Federal University of Minas Gerais, Belo Horizonte, Brazil.|State University of Minas Gerais, Ibirité, Brazil.
authors.forename: Juliana Bohnen
authors.initials: JB
authors.lastname: Guimarães
authors.affiliation: Department of Physiology and Biophysics, Institute of Biological Sciences, Federal University of Minas Gerais, Belo Horizonte, Brazil.
authors.forename: Cândido Celso
authors.initials: CC
authors.lastname: Coimbra
mesh_terms: D000818:Animals; D001120:Arginine / Q000008:administration & dosage* / Q000378:metabolism; D001831:Body Temperature / Q000187:drug effects / Q000502:physiology; D001833:Body Temperature Regulation / Q000187:drug effects / Q000502:physiology*; D001921:Brain / Q000187:drug effects / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D007276:Injections, Intraventricular; D008297:Male; D010805:Physical Conditioning, Animal / Q000379:methods / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D012420:Running / Q000502:physiology*; D012881:Skin Temperature / Q000187:drug effects / Q000502:physiology*
chemical_list: D001120:Arginine
keywords: body temperature; fatigue; nitric oxide; physical performance; skin; thermoregulation; treadmill