AJP - Heart and Circulatory Physiology, Vol 253, Issue 2 394-H401, Copyright © 1987 by American Physiological Society
Atrioventricular responses of canine heart following chronic unilateral vagotomy
D. V. Priola, C. Anagnostelis, C. Sanchez-Wilson and T. M. Blomquist
The intrinsic cardiac nerves (ICN) have been shown to develop
supersensitivity to nicotine (NIC) following complete extrinsic cardiac
denervation. The present experiments were performed to delineate the
pattern of ICN distribution in the heart by examining the pattern of NIC
supersensitivity after unilateral vagotomy (VGX). Thirty-eight dogs were
placed on cardiopulmonary bypass and inotropy evaluated by means of
isovolumic pressures from fluid-filled balloons placed in the atria and
ventricles. The animals were divided into three groups: group I,
sham-operated controls; group II, animals studied 1-2 wk after VGX; and
group III, animals studied 8-12 wk after VGX. Chronotropic and inotropic
responses were evaluated in terms of NIC and acetylcholine (ACh)
dose-response curves as well as frequency-response curves to stimulation of
the intact vagus nerve (0.5-30 Hz). No change in NIC sensitivity was
observed in group II, and vagal frequency-response curves were identical to
group I. In group III dogs, both the right atrium and right ventricle
showed significant increases in NIC sensitivity after left vagotomy. All
group III animals showed right-shifted frequency-response curves. We
conclude that nicotinic supersensitivity of the ICN and inotropic
unresponsiveness to vagal stimulation occur but are slow in developing
(70-130 days); and preganglionic sprouting does not appear to play a
functional role in the adjustment of cardiac control mechanisms to
unilateral vagotomy.
