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Muscarinic cholinoceptors in the ventromedial hypothalamic nucleus (VMH) facilitate tail heat loss during exercise
Author(s) -
Wanner Samuel Penna,
Guimarães Juliana Bohnen,
Rodrigues Luiz Oswaldo Carneiro,
Marubayashi Umeko,
Coimbra Cândido Celso,
Lima Nilo Resende Viana
Publication year - 2007
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.21.5.a579-d
Subject(s) - endocrinology , medicine , muscarinic acetylcholine receptor , chemistry , vasodilation , core temperature , acetylcholine , receptor
The aim of this study was to evaluate the participation of muscarinic cholinoceptors in the VMH on heat balance and central fatigue during treadmill exercise (24 m.min −1 , 5% inclination). Under anesthesia, the rats were fitted with bilateral cannulas into the VMH one week prior to the experiments. Tail skin (T tail ) and core body temperature (T b ) were measured after the injection of 200 ηL of 5 × 10 −9 mol methylatropine (Atr) or 0.15 M NaCl solution (Sal). Atr injection into the VMH greatly increased heat storage rate (HSR) measured until fatigue (19.7 ± 4.6 cal.min −1 Atr vs. 9.7 ± 3.3 cal.min −1 Sal; P < 0.05) and attenuated the exercise‐induced tail vasodilation as seen by T tail (23.98 ± 0.43° C Atr vs. 25.52 ± 0.85° C Sal; P < 0.05), indicating an inhibition of the heat loss process. The increased T b threshold and the 2 min delay for trigger the heat loss mechanisms observed in Atr‐treated rats are associated with increased heat storage and may be responsible for the decreased running performance of these animals (21.0 ± 2.9 min Atr vs. 33.5 ± 3.4 min Sal; n = 8; P < 0.001). In fact, we have observed a close negative correlation between HSR and time to fatigue (r = −0.63; P < 0.01). We conclude that muscarinic cholinoceptors in the VMH facilitate heat loss mechanisms, through tail skin vasodilation, and a delay in this adjustment would decrease physical exercise performance due an excess of heat storage.