AJP - Heart and Circulatory Physiology, Vol 271, Issue 1 44-H50, Copyright © 1996 by American Physiological Society

ARTICLES

Parasympathetic inhibition of sympathetic effects on sinus rate in anesthetized dogs

Y. Furukawa, Y. Hoyano and S. Chiba
Department of Pharmacology, Shinshu University School of Medicine, Matsumoto, Japan.

The intracardiac parasympathetic neural elements that control sinus rate are found in the fatty tissue overlying the atrial junctions of the right pulmonary veins of mammalian hearts. We refer to these nerves as the sinus rate-related parasympathetic nerves (SRRPN). Thus, to elucidate the role of SRRPN, we studied the effects of cervical vagus stimulation on the positive chronotropic responses to cardiac sympathetic nerve stimulation and isoproterenol infusion before and after the SRRPN were removed in the open-chest anesthetized dog heart. Before SRRPN denervation, cervical vagus stimulation suppressed the sinus rate and the positive chronotropic response to sympathetic nerve stimulation or isoproterenol infusion. After SRRPN denervation, cervical vagus stimulation hardly decreased the sinus rate. On the other hand, even after SRRPN denervation, cervical vagus stimulation suppressed the rate increased by sympathetic stimulation. Cervical vagus stimulation also attenuated the sinus rate increased by isoproterenol. The inhibition by vagus stimulation of the chronotropic response to sympathetic stimulation was greater than that of the response to isoproterenol. The attenuation by cervical vagus stimulation was abolished by atropine. These results suggest that 1) a small number of vagus nerves to the sinoatrial nodal area different from the SRRPN decrease the sinus rate increased by adrenergic interventions and 2) the same activation that causes relatively small effects on sinus rate is capable of causing much larger changes in sinus rate during increased sympathetic tone or in the case of beta-adrenoceptor agonist treatment in the heart in situ.

This article has been cited by other articles:

				M. Waldmann, G. W. Thompson, G. C. Kember, J. L. Ardell, and J. A. Armour Stochastic behavior of atrial and ventricular intrinsic cardiac neurons J Appl Physiol, August 1, 2006; 101(2): 413 - 419. [Abstract] [Full Text] [PDF]

				D. C. Randall, D. R. Brown, A. S. McGuirt, G. W. Thompson, J. A. Armour, and J. L. Ardell Interactions within the intrinsic cardiac nervous system contribute to chronotropic regulation Am J Physiol Regulatory Integrative Comp Physiol, November 1, 2003; 285(5): R1066 - R1075. [Abstract] [Full Text] [PDF]

				M. Tsuboi, Y. Furukawa, K. Nakajima, F. Kurogouchi, and S. Chiba Inotropic, chronotropic, and dromotropic effects mediated via parasympathetic ganglia in the dog heart Am J Physiol Heart Circ Physiol, September 1, 2000; 279(3): H1201 - H1207. [Abstract] [Full Text] [PDF]

				D. C. Randall, D. R. Brown, S.-G. Li, M. E. Olmstead, J. M. Kilgore, A. G. Sprinkle, W. C. Randall, and J. L. Ardell Ablation of posterior atrial ganglionated plexus potentiates sympathetic tachycardia to behavioral stress Am J Physiol Regulatory Integrative Comp Physiol, September 1, 1998; 275(3): R779 - R787. [Abstract] [Full Text] [PDF]

				M. Hirose, Y. Furukawa, Y. Nagashima, M. Lakhe, and S. Chiba Pituitary Adenylate Cyclase-Activating Polypeptide-27 Causes a Biphasic Chronotropic Effect and Atrial Fibrillation in Autonomically Decentralized, Anesthetized Dogs J. Pharmacol. Exp. Ther., November 1, 1997; 283(2): 478 - 487. [Abstract] [Full Text]

				Y. Hoyano, Y. Furukawa, M. Kasama, and S. Chiba Parasympathetic inhibition of sympathetic effects on atrioventricular conduction in anesthetized dogs Am J Physiol Heart Circ Physiol, October 1, 1997; 273(4): H1800 - H1806. [Abstract] [Full Text] [PDF]