Neurohumoral responses during prolonged exercise in humans

• Published in: JOURNAL OF APPLIED PHYSIOLOGY Vol. 95; no. 3; pp. 1125 - 1131
• Main Authors: Nybo, Lars, Nielsen, Bodil, Blomstrand, Eva, Moller, Kirsten, Secher, Niels
• Format: Journal Article Publication
• Language: English
• Published: Bethesda, MD Am Physiological Soc 01.09.2003; American Physiological Society
• Subjects: Adult; Biological and medical sciences; Blood Gas Analysis; Blood Glucose - metabolism; Body Temperature - physiology; Brain; Brain Chemistry - physiology; Carbohydrates; Cerebrovascular Circulation; Dietary Carbohydrates - metabolism; Dopamine - metabolism; Exercise; Exercise - physiology; Exercise Test; Fundamental and applied biological sciences. Psychology; Fysiologi; Fysiologi och farmakologi; Human subjects; Humans; Male; MEDICIN; MEDICINE; Muscle Fatigue - physiology; Neurotransmitter Agents - metabolism; Oxygen Consumption - physiology; Physiology; Physiology and pharmacology; Temperature; Tryptophan - metabolism; Tyrosine - metabolism; Vertebrates: body movement. Posture. Locomotion. Flight. Swimming. Physical exercise. Rest. Sports; Physical exercise; Human; Dopamine; Body temperature; Central nervous system; Bicycle ergometer; Neuroendocrine regulation; Tryptophan; Catecholamine; brain; Recovery; Encephalon; Aminoacid; Dopamine agonist; Neurotransmitter; Hyperthermia; Prolonged
• ISSN: 8750-7587; 1522-1601; 1522-1601
• DOI: 10.1152/japplphysiol.00241.2003

1 Department of Human Physiology, Institute of Exercise and Sport Sciences, August Krogh Institute, and Departments of 3 Infection Diseases and 4 Anesthesia, Rigshospitalet, The Copenhagen Muscle Research Center, University of Copenhagen, DK-2100 Copenhagen, Denmark; and 2 University College of Physical Education and Sports and Department of Physiology and Pharmacology, Karolinska Institute, SE-171 77 Stockholm, Sweden Submitted 7 March 2003 ; accepted in final form 27 April 2003 This study examined neurohumoral alterations during prolonged exercise with and without hyperthermia. The cerebral oxygen-to-carbohydrate uptake ratio (O 2 /CHO = arteriovenous oxygen difference divided by arteriovenous glucose difference plus one-half lactate), the cerebral balances of dopamine, and the metabolic precursor of serotonin, tryptophan, were evaluated in eight endurance-trained subjects during exercise randomized to be with or without hyperthermia. The core temperature stabilized at 37.9 ± 0.1°C (mean ± SE) in the control trial, whereas it increased to 39.7 ± 0.2°C in the hyperthermic trial, with a concomitant increase in perceived exertion ( P < 0.05). At rest, the brain had a small release of tryptophan (arteriovenous difference of -1.2 ± 0.3 µmol/l), whereas a net balance was obtained during the two exercise trials. Both the arterial and jugular venous dopamine levels became elevated during the hyperthermic trial, but the net release from the brain was unchanged. During exercise, the O 2 /CHO was similar across trials, but, during recovery from the hyperthermic trial, the ratio decreased to 3.8 ± 0.3 ( P < 0.05), whereas it returned to the baseline level of 6 within 5 min after the control trial. The lowering of O 2 /CHO was established by an increased arteriovenous glucose difference (1.1 ± 0.1 mmol/l during recovery from hyperthermia vs. 0.7 ± 0.1 mmol/l in control; P < 0.05). The present findings indicate that the brain has an increased need for carbohydrates during recovery from strenuous exercise, whereas enhanced perception of effort as observed during exercise with hyperthermia was not related to alterations in the cerebral balances of dopamine or tryptophan. brain; dopamine; hyperthermia; tryptophan Address for reprint requests and other correspondence: L. Nybo, Dept. of Human Physiology, Institute of Exercise and Sport Sciences, August Krogh Institute, Universitetsparken 13, DK-2100 Copenhagen Ø, Denmark (E-mail: lnnielsen{at}aki.ku.dk ).