Responses to exercise in the heat related to measures of hypothalamic serotonergic and dopaminergic function.
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-HT(1A)) agonist, dopaminergic D(2) antagonist] neuroendocrine challenge, with and without pretreatment with pindolol (5-HT(1A) 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 (VO(2max)) until volitional fatigue at 35 degrees 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.
Bridge
Mathew W
MW
School of Sport and Exercise Sciences, The University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK. m.w.bridge@bham.ac.uk
Weller
Andrew S
AS
Rayson
Mark
M
Jones
David A
DA
D000222:Adaptation, Physiological / Q000187:drug effects / Q000502:physiology; D000328:Adult; D001786:Blood Glucose / Q000378:metabolism*; D001833:Body Temperature Regulation / Q000187:drug effects / Q000502:physiology*; D002065:Buspirone / Q000494:pharmacology; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D017079:Exercise Tolerance / Q000187:drug effects / Q000502:physiology*; D006358:Hot Temperature; D006801:Humans; D007031:Hypothalamus / Q000187:drug effects / Q000378:metabolism*; D019344:Lactic Acid / Q000097:blood; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology; D010807:Physical Endurance / Q000187:drug effects / Q000502:physiology; D010869:Pindolol / Q000494:pharmacology; D044282:Receptor, Serotonin, 5-HT1A / Q000097:blood / Q000378:metabolism*; D017448:Receptors, Dopamine D2 / Q000819:agonists / Q000097:blood / Q000378:metabolism*; D058829:Serotonin 5-HT1 Receptor Antagonists; D012881:Skin Temperature / Q000187:drug effects / Q000502:physiology; D013546:Sweating / Q000502:physiology
D001786:Blood Glucose; D017448:Receptors, Dopamine D2; D058829:Serotonin 5-HT1 Receptor Antagonists; D044282:Receptor, Serotonin, 5-HT1A; D019344:Lactic Acid; D010869:Pindolol; D002065:Buspirone