Increased brain l‐arginine availability facilitates cutaneous heat loss induced by running exercise |
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Authors: | Samuel Penna Wanner Laura Hora Rios Leite Juliana Bohnen Guimarães Cândido Celso Coimbra |
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Institution: | 1. Department of Physiology and Biophysics, Institute of Biological Sciences, Federal University of Minas Gerais, Belo Horizonte, Brazil;2. Exercise Physiology Laboratory, School of Physical Education, Physiotherapy and Occupational Therapy, Federal University of Minas Gerais, Belo Horizonte, Brazil;3. Department of Physiology, Institute of Biological Sciences, Federal University of Juiz de Fora, Juiz de Fora, Brazil;4. State 5. University of Minas Gerais, Ibirité, Brazil |
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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. |
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Keywords: | body temperature fatigue nitric oxide physical performance skin thermoregulation treadmill |
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