title: Responses to exercise in the heat related to measures of hypothalamic serotonergic and dopaminergic function.
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-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.
authors.affiliation: School of Sport and Exercise Sciences, The University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK. m.w.bridge@bham.ac.uk
authors.forename: Mathew W
authors.initials: MW
authors.lastname: Bridge
authors.forename: Andrew S
authors.initials: AS
authors.lastname: Weller
authors.forename: Mark
authors.initials: M
authors.lastname: Rayson
authors.forename: David A
authors.initials: DA
authors.lastname: Jones
mesh_terms: 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
chemical_list: 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