AJP - Regulatory, Integrative and Comparative Physiology, Vol 248, Issue 5 515-R523, Copyright © 1985 by American Physiological Society
Autonomic modulation of refractoriness in canine specialized His-Purkinje system
L. A. Turner, E. J. Zuperku, Z. J. Bosnjak and J. P. Kampine
The effects of autonomic efferent stimulation on refractoriness of the
specialized His-Purkinje system were examined in open-chest dogs
anesthetized with 1.0% halothane. In eight animals submaximal bilateral
stimulation of the ventral ansae subclavia decreased (P less than or equal
to 0.01) the average functional refractory period for the propagation of
His bundle extrastimuli to five ventricular recording sites (HP-FRP) by
10.9 +/- 0.6 ms. Submaximal stimulation of the decentralized vagal nerves
that produced first degree atrioventricular block did not affect
ventricular refractoriness. Combined vagosympathetic stimulation produced a
smaller (P less than or equal to 0.01) decrease of the average HP-FRP (7.2
+/- 1.1 ms) than that produced by sympathetic stimulation alone.
Administration of atropine abolished (P less than or equal to 0.05) vagal
antagonism of the shortening effect of isoproterenol on the average HP-FRP.
Treatment with propranolol reversed (P less than or equal to 0.01) the
sympathetic effect on the average HP-FRP and nonuniformly increased
refractoriness in the His-Purkinje system. The latter changes were
abolished (P less than or equal to 0.05) by infusion of phentolamine. The
autonomic nervous system modulates His-Purkinje refractoriness by actions
mediated by cholinergic and both alpha- and beta-adrenergic receptors.
