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Evidence that brain L‐arginine availability modulates heat loss during physical exercise in rats
Author(s) -
Wanner Samuel Penna,
Leite Laura Hora Rios,
Marubayashi Umeko,
Coimbra Cândido Celso
Publication year - 2008
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.22.1_supplement.956.12
Subject(s) - ketamine , ventricle , chemistry , endocrinology , arginine , medicine , core temperature , nitric oxide , zoology , anesthesia , biochemistry , biology , amino acid
We investigated the effects of increased brain L‐arginine (precursor of nitric oxide synthesis) availability on thermoregulatory adjustments and physical performance in rats during exercise (18 m.min ‐1 and 5% inclination) until fatigue. Under anesthesia with ketamine and xylazine, male Wistar rats received implants of a guide cannula into the right lateral cerebral ventricle and of a temperature probe into the peritoneal cavity. On the day of the experiments, core (T b ) and tail skin temperatures were measured while the rats were running after injection of 2 μL of either NaCl 0.15 M (Sal, n = 11) or L‐arginine solution (L‐arg: 0.82 M, n = 6; 1.65 M, n = 6, and 3.30 M, n = 5) into the cerebral ventricle. Heat storage rate and threshold T b for tail vasodilation (TT b V) were calculated. L‐arg injection induced a dose‐dependent reduction in the TT b V and heat storage rate (3.23 ± 0.84 cal.min −1 , L‐arg 3.30 M; 6.46 ± 1.12 cal.min −1 , L‐arg 1.65 M; 8.59 ± 0.95 cal.min −1 , L‐arg 0.82 M; 9.54 ± 0.94 cal.min −1 , Sal; p<0.05). Although the lower T b at fatigue point, treatment with L‐arg failed to change exercise performance (25.7 ± 3.5 min, L‐arg 3.30 M; 25.7 ± 2.4 min, L‐arg 1.65 M; 26.4 ± 2.9 min, L‐arg 0.82 M; 26.9 ± 1.7 min, Sal). These results indicate that brain nitric oxide transmission modulates heat loss during exercise, probably by reducing sympathetic vasoconstrictor tonus to skin vessels. Supported by: CNPq, FAPEMIG e CAPES.