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This Article Full Text Full Text (PDF) All Versions of this Article: 577/2/717    most recent jphysiol.2006.116426v1 Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Hart, E. Articles by Shave, R. Search for Related Content PubMed PubMed Citation Articles by Hart, E. Articles by Shave, R. Related Collections Integrative

¹ Centre for Sports Medicine and Human Performance, Brunel University, London, UK
² Copenhagen Muscle Research Centre, Department of Anaesthesia, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
³ Research Institute for Sports and Exercise Science, John Moores University, Liverpool
⁴ English Institute of Sport, London

Desensitization of the ß-adrenoreceptors (ß-AR) may contribute to a post-exercise reduction in left ventricular (LV) function. However, attenuation of the chronotropic and inotropic responses to a ß-AR agonist may depend upon alterations in parasympathetic tone. Furthermore, changes in cardiac output and LV diastolic function in response to a ß-AR agonist, pre- to post-prolonged exercise, remain unclear. Seven trained males (mean ± S.D., age 27 ± 6 years) performed 4 h of ergometer rowing. Peak heart rate (HR) and LV systolic and diastolic functional responses to incremental isoproterenol (isoprenaline) infusion (2, 4 and 6 µg kg min^–1) were assessed after vagal blockade (glycopyrrolate, 1.2 mg). LV systolic function was assessed by the pressure/volume ratio (systolic blood pressure/end systolic volume) and , whilst diastolic function was evaluated as peak early and late transmitral filling velocities. Following exercise, the pressure/volume ratio decreased by 25% (P < 0.05), whereas was unchanged (P > 0.05). The early/late filling ratio was reduced by 36% after exercise, due to an elevation in late LV filling (P < 0.01). The increase in HR response to isoproterenol infusion was blunted post-exercise at both 4 and 6 µg kg min^–1 (127 ± 7 and 132 ± 6 beats min^–1) compared with pre-exercise (138 ± 8 and 141 ± 12 beats min^–1, P < 0.05). Additionally, the pressure/volume ratio and were blunted post-exercise in response to isoproterenol (P < 0.05). In contrast, diastolic function was similar before and after exercise during isoproterenol infusion (P > 0.05). Desensitization of the ß-AR contributes to an attenuated left ventricular systolic but not diastolic function following prolonged exercise.

(Received 3 July 2006; accepted after revision 8 September 2006; first published online 14 September 2006)
Corresponding author R. Shave: Centre for Sports Medicine and Human Performance, Brunel University, Uxbridge, Middlesex UB8 3PH, UK.  Email: rob.shave{at}brunel.ac.uk