Erschienen in:
01.06.2003 | Original Article
Responses to exercise in the heat related to measures of hypothalamic serotonergic and dopaminergic function
verfasst von:
Mathew W. Bridge, Andrew S. Weller, Mark Rayson, David A. Jones
Erschienen in:
European Journal of Applied Physiology
|
Ausgabe 5/2003
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Abstract
We have studied 12 recreationally active men to measure their responses to exercise in the heat and relate these to measures of hypothalamic function explored with a buspirone [5-hydroxytryptamine 1A (5-HT1A) agonist, dopaminergic D2 antagonist] neuroendocrine challenge, with and without pretreatment with pindolol (5-HT1A antagonist). Pindolol treatment allowed the serotonergic and non-serotonergic components of prolactin release to be distinguished. Subjects exercised at 73 (5)% maximal rate of oxygen uptake (V̇O2max) until volitional fatigue at 35°C (relative humidity, 30%). On another two occasions they underwent a buspirone challenge [0.5 mg (kg body mass)−1], once with, and once without, pindolol [0.5 mg (kg body mass)−1] pretreatment and the circulating plasma concentrations of prolactin were measured for the next 2.5 h. Rectal temperature increased throughout exercise, whilst mean skin temperature remained constant. There was a wide inter-subject variation in prolactin response to the neuroendocrine challenges. The proportion of the prolactin response to buspirone attributable to a non-serotonergic component (most likely dopaminergic) correlated both with exercise duration (r=0.657, P=0.028), rectal temperature at fatigue (r=0.623, P=0.041) and the rate of temperature rise (r=−0.669, P=0.024). Our results suggest that high activity of the dopaminergic pathways in the hypothalamus is a predictor of exercise tolerance in the heat.