Responses to exercise in the heat related to measures of hypothalamic serotonergic and dopmaninergic function
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Colleges, School and Institutes
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 D-2 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 ((V) over dot O-2max) until volitional fatigue at 35degreesC (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 (ka 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.
|Number of pages||9|
|Journal||European journal of applied physiology|
|Publication status||Published - 1 Jun 2003|
- serotonin, heat tolerance, dopamine, prolactin, fatigue