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Pacemaker shift in the rabbit sinoatrial node in response to vagal nerve stimulation

Published online by Cambridge University Press:  31 July 2001

Nitaro Shibata ,
Shin Inada ,
Kazuyuki Mitsui ,
Haruo Honjo ,
Mitsuru Yamamoto ,
Ryoko Niwa ,
Mark R. Boyett  and
Itsuo Kodama
Nitaro Shibata
Affiliation:
Departments of Circulation and Humoral Regulation, Research Institute of Environmental Medicine, Nagoya University, Nagoya 464-8601, Japan, Department of Cardiology, The Heart Institute of Japan, Tokyo Women's Medical College, Tokyo 162-0054, Japan, School of Engineering, Tokyo Denki University, Tokyo 101-8457, Japan and School of Biomedical Sciences, University of Leeds, Leeds LS2 9JT, UK
Shin Inada
Affiliation:
Departments of Circulation and Humoral Regulation, Research Institute of Environmental Medicine, Nagoya University, Nagoya 464-8601, Japan, Department of Cardiology, The Heart Institute of Japan, Tokyo Women's Medical College, Tokyo 162-0054, Japan, School of Engineering, Tokyo Denki University, Tokyo 101-8457, Japan and School of Biomedical Sciences, University of Leeds, Leeds LS2 9JT, UK
Kazuyuki Mitsui
Affiliation:
Departments of Circulation and Humoral Regulation, Research Institute of Environmental Medicine, Nagoya University, Nagoya 464-8601, Japan, Department of Cardiology, The Heart Institute of Japan, Tokyo Women's Medical College, Tokyo 162-0054, Japan, School of Engineering, Tokyo Denki University, Tokyo 101-8457, Japan and School of Biomedical Sciences, University of Leeds, Leeds LS2 9JT, UK
Haruo Honjo
Affiliation:
Departments of Circulation and Humoral Regulation, Research Institute of Environmental Medicine, Nagoya University, Nagoya 464-8601, Japan, Department of Cardiology, The Heart Institute of Japan, Tokyo Women's Medical College, Tokyo 162-0054, Japan, School of Engineering, Tokyo Denki University, Tokyo 101-8457, Japan and School of Biomedical Sciences, University of Leeds, Leeds LS2 9JT, UK
Mitsuru Yamamoto
Affiliation:
Departments of Circulation and Humoral Regulation, Research Institute of Environmental Medicine, Nagoya University, Nagoya 464-8601, Japan, Department of Cardiology, The Heart Institute of Japan, Tokyo Women's Medical College, Tokyo 162-0054, Japan, School of Engineering, Tokyo Denki University, Tokyo 101-8457, Japan and School of Biomedical Sciences, University of Leeds, Leeds LS2 9JT, UK
Ryoko Niwa
Affiliation:
Departments of Circulation and Humoral Regulation, Research Institute of Environmental Medicine, Nagoya University, Nagoya 464-8601, Japan, Department of Cardiology, The Heart Institute of Japan, Tokyo Women's Medical College, Tokyo 162-0054, Japan, School of Engineering, Tokyo Denki University, Tokyo 101-8457, Japan and School of Biomedical Sciences, University of Leeds, Leeds LS2 9JT, UK
Mark R. Boyett
Affiliation:
Departments of Circulation and Humoral Regulation, Research Institute of Environmental Medicine, Nagoya University, Nagoya 464-8601, Japan, Department of Cardiology, The Heart Institute of Japan, Tokyo Women's Medical College, Tokyo 162-0054, Japan, School of Engineering, Tokyo Denki University, Tokyo 101-8457, Japan and School of Biomedical Sciences, University of Leeds, Leeds LS2 9JT, UK
Itsuo Kodama
Affiliation:
Departments of Circulation and Humoral Regulation, Research Institute of Environmental Medicine, Nagoya University, Nagoya 464-8601, Japan, Department of Cardiology, The Heart Institute of Japan, Tokyo Women's Medical College, Tokyo 162-0054, Japan, School of Engineering, Tokyo Denki University, Tokyo 101-8457, Japan and School of Biomedical Sciences, University of Leeds, Leeds LS2 9JT, UK
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Abstract

Effects of brief postganglionic vagal nerve stimulation on the activation sequence of the rabbit sinoatrial (SA) node were investigated. Activation sequences in a small area (7 mm × 7 mm) on the epicardial surface were measured in a beat-to-beat manner using an extracellular potential mapping system composed of 64 modified bipolar electrodes with high-gain and low-frequency band-pass filtering. The leading pacemaker site was recognised clearly from both the activation sequence and the characteristic morphology of the potentials. Vagal stimulation resulted in a short-lasting initial slowing of spontaneous rate followed by a long-lasting secondary slowing; a brief period of relative or absolute acceleration was interposed between the two slowing phases. During these changes of spontaneous rate, the leading pacemaker site shifted in a complex beat-to-beat manner by 1-6 mm alongside the crista terminalis in the superior or inferior direction. For the first spontaneous excitation following stimulation, the greater the slowing, the larger the distance of the pacemaker shift. There was no such linear relationship between the extent of slowing and the distance of pacemaker shift for the subsequent beats. These changes in the leading pacemaker site in response to vagal stimulation may be the result of the functional and morphological heterogeneity of the mammalian SA node in terms of innervation, receptor distribution and ion channel densities. Experimental Physiology (2001) 86.2, 177-184.

Type
Research Article
Information
Experimental Physiology , Volume 86 , Issue 2 , March 2001 , pp. 177 - 184
Copyright
© The Physiological Society 2001

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