Cookies on this website

We use cookies to ensure that we give you the best experience on our website. If you click 'Accept all cookies' we'll assume that you are happy to receive all cookies and you won't see this message again. If you click 'Reject all non-essential cookies' only necessary cookies providing core functionality such as security, network management, and accessibility will be enabled. Click 'Find out more' for information on how to change your cookie settings.

1. Cardiac chronotropic responses to isoprenaline are reduced with ageing in man. It is unclear whether this is due to reduced cardiac beta-adrenergic sensitivity or to age-associated differences in reflex cardiovascular responses to the vasodilatory effects of isoprenaline. Age-associated changes in physical activity are also reported to influence beta-adrenergic sensitivity. 2. The aim of the present study was to determine the contribution of alterations in reflex changes in para-sympathetic and sympathetic influences and physical fitness to the age-associated reduction in cardiac chronotropic responses to beta-adrenergic agonists. 3. The effect of 'autonomic blockade' with atropine (40 micrograms/kg intravenously) and clonidine (4 micrograms/kg intravenously) on blood pressure, heart rate and chronotropic responses to intravenous bolus isoprenaline doses was determined in eight healthy young (mean age 21 years), nine healthy elderly (72 years) and 10 endurance-trained elderly (69 years) subjects. 4. Elderly subjects had a reduced increase in heart rate after atropine (young, 49 +/- 9 beats/min; elderly, 36 +/- 5 beats/min; endurance-trained elderly, 34 +/- 12 beats/min; P < 0.01) and did not demonstrate the transient increase in systolic blood pressure after clonidine observed in young subjects (young, 11 +/- 10 mmHg; elderly, -12 +/- 16 mmHg; endurance-trained elderly, -18 +/- 11 mmHg; P < 0.01). 5. Cardiac chronotropic sensitivity to isoprenaline after 'autonomic blockade' increased in the young but decreased in the elderly subjects.(ABSTRACT TRUNCATED AT 250 WORDS)


Journal article


Clin Sci (Lond)

Publication Date





297 - 302


Adult, Age Factors, Aged, Aged, 80 and over, Atropine, Autonomic Nervous System, Blood Pressure, Clonidine, Heart, Heart Rate, Hemodynamics, Humans, Isoproterenol, Male, Physical Endurance, Stimulation, Chemical