Nitric oxide modulates signalling between cultured adult peripheral
cardiac neurons and cardiomyocytes.
Horackova, M., J. A. Armour, D. A. Hopkins, and M. H. Huang.
Department of Physiology and Biophysics, Department of Anatomy and
Neurobiology, Faculty of Medicine, Dalhousie University, Halifax,
Nova Scotia B3H 4H7, Canada
APStracts 2:0136C, 1995.
To determine whether nitric oxide (NO) modifies cardiomyocytes
directly or indirectly via peripheral autonomic neurons, the effects
of NO were studied in long-term (3-6 weeks) cultures of adult guinea
-pig ventricular myocytes alone as well as in cocultures with adult
extracardiac (stellate ganglion) or intrinsic cardiac neurons. NADPH
diaphorase was associated histochemically with cultured intrinsic
cardiac and, to a lesser extent, stellate ganglion neurons. The
beating frequency of ventricular myocytes cocultured with intrinsic
cardiac neurons (M-intrinsic) or stellate ganglion neurons (M
-stellate) increased by 20-30% (P < 0.001) following administration
of the NO donor SNAP; this effect was abolished by the guanylate
cyclase inhibitor LY 83583. The beating frequency of noninnervated
myocyte cultures was not affected by SNAP. The precursor of NO, L
-arginine also increased the beating rate (20%; P < 0.05) of M
-intrinsic cocultures, not affecting that of M-stellate cocultures or
noninnervated myocyte cultures. Augmentor effects induced by SNAP
were no longer elicited in the presence of TTX, and were unaffected
by [beta]-adrenergic or muscarinic receptor blockade. It is concluded
that (1) NO-sensitive neurons are present in stellate and intrinsic
cardiac ganglia and these neurons increase the beating rate of
cardiomyocytes in the presence of NO; (2) more NO-synthesizing
neurons are present in M-intrinsic than M-stellate cocultures as L
-arginine increased the beating frequency of myocytes significantly
only in M-intrinsic cocultures. (3) The beating rate of noninnervated
myocyte cultures is not directly affected by NO.
Received 9 November 1994; accepted in final form 28 February
1995.
APS Manuscript Number C665-4.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 21 March 1995.