Proceedings of The Physiological Society
University of Manchester (2010) Proc Physiol Soc 19, PC275
Acute exercise modulates bitter but not salt taste perception in untrained healthy subjects
J. Cartwright1, J. Butler1, D. Raby1, S. Riddell1, J. K. Melichar1, L. F. Donaldson1
1. Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom.
Increasing the level of available noradrenaline in healthy subjects, using specific reuptake inhibitor drugs results in a decrease in bitter and sour thresholds with no change in salt threshold . Type III (salt/sour) taste cells do not synthesise catecholamines, but can take up noradrenaline, and repackage and release it as a neurotransmitter .These observations suggest that noradrenaline may have a roles in taste-specific modulation of taste threshold. In addition there is a significant relationship between taste and long-term anxiety level, in that as anxiety increases, taste becomes more blunted . Five to ten minutes of heavy exercise in normotensive untrained healthy young adults results in an 8-fold increase in circulating catecholamines, with little hypothalamic-pituitary-adrenal activation . This study used brief heavy exercise to investigate the effect of an increase in circulating catecholamines on bitter and salt taste perception. Bitter and salt recognition thresholds were determined in 23 healthy volunteers (18-26 years, 9 male, 14 female) at the tip of the tongue at each of two experimental sessions, consisting of heavy exercise (300W, 5-10 min) and the same period of quiet rest. Different concentrations of quinine hydrochloride (1mM - 1µM) and sodium chloride (100mM - 1mM) solutions were presented to each subject in a pseudorandom order, using cotton buds soaked in each solution. Each taste concentration was presented a minimum of 5 times before and after intervention in each of the two sessions. Psychophysical taste functions were constructed to calculate mean bitter and salt recognition threshold before and after exercise and rest. Change in taste hedonics (pleasantness) and intensity were also measured to suprathreshold salt and quinine HCl solutions using a generalised labelled magnitude scale with each intervention. Protocols were approved by the Faculty of Medical and Veterinary Sciences Ethics Committee, University of Bristol. There was a significant drop in bitter recognition threshold after exercise (before: 386µM (204 to 731µM (95% CI)); after 133µM (65 to 270µM), p=0.03, F test), but rest had no significant effect (before: 434µM (222 to 849µM); after: 257µM (99 to 665µM), p=0.4, F test). Only rest and not exercise resulted in a reduction in salt threshold (before 53mM (44 to 64mM); after 37mM (28 to 47mM), p=0.02, F test). Both exercise and rest changed perceived pleasantness or strength of suprathreshold quinine or salt solutions to the same extent. In heavy exercise, when sympathetics in this non-exercising muscle (tongue) may release noradrenaline, the increased available noradrenaline may enhance neurotransmission in taste cells, reducing bitter taste threshold.
Where applicable, experiments conform with Society ethical requirements