Autoregulation of cardiac output is overcome by adrenergic stimulation in the anaconda heart

Most vertebrates increase cardiac output during activity by elevating heart rate with relatively stable stroke volume. However, several studies have demonstrated 'intrinsic autoregulation' of cardiac output where artificially increased heart rate is associated with decreased stroke volume,...

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Bibliographic Details
Published in:Journal of experimental biology Vol. 220; no. Pt 3; pp. 336 - 340
Main Authors: Joyce, William, Axelsson, Michael, Wang, Tobias
Format: Journal Article
Language:English
Published: England 01.02.2017
Subjects:
Adrenergic alpha-Agonists - metabolism
Animals
Boidae - physiology
Cardiac Output
Heart - physiology
Homeostasis
Male
Myocardial Contraction
Norepinephrine - metabolism
Stroke Volume
Heart rate
Cardiovascular
Noradrenaline
Stroke volume
ISSN:1477-9145
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Summary:Most vertebrates increase cardiac output during activity by elevating heart rate with relatively stable stroke volume. However, several studies have demonstrated 'intrinsic autoregulation' of cardiac output where artificially increased heart rate is associated with decreased stroke volume, leaving cardiac output unchanged. We explored the capacity of noradrenaline to overcome autoregulation in the anaconda heart. Electrically pacing in situ perfused hearts from the intrinsic heart rate to the maximum attainable resulted in a proportional decrease in stroke volume. However, noradrenaline, which increased heart rate to the same frequency as pacing, maintained stroke volume and thus increased cardiac output. In atrial and ventricular preparations, noradrenaline significantly increased the force of contraction and contraction kinetics. Thus, the increased contractility associated with adrenergic stimulation ameliorates filling limitations at high heart rates. Although heart rate appears the primary regulated variable during activity, this may only be achieved with compensatory amendments in myocardial contractility provided by adrenergic stimulation.
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ISSN:1477-9145
DOI:10.1242/jeb.149237