Inhibition of sarcoplasmic reticulum Ca2+-ATPase decreases atrioventricular node-paced heart rate in rabbits |
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| Authors: | Cheng Hongwei Smith Godfrey L Orchard Clive H Hancox Jules C Burton Francis L |
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| Institution: | H. Cheng and F. L. Burton: Institute of Cardiovascular & Medical Sciences, Room 406, West Medical Building, University of Glasgow, Glasgow G12 8QQ, UK. ?? francis.burton@glasgow.ac.uk. |
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| Abstract: | Recent data indicate that Ca(2+) cycling in isolated atrioventricular node (AVN) cells contributes to setting spontaneous rate. The aim of the present study was to extend this observation to the intact AVN in situ, by evaluating the effects of inhibiting sarcoplasmic reticulum Ca(2+) uptake with cyclopiazonic acid (CPA) on intact AVN spontaneous activity and its response to isoprenaline. A model of the AVN-paced heart was produced to investigate intact AVN automaticity, by surgical ablation of the sino-atrial node (SAN) in the rabbit Langendorff-perfused heart. Electrograms were recorded from a site close to the AVN (triangle of Koch), an atrial site above the AVN, the left atrium and right ventricle, enabling AVN pacing of the preparation to be confirmed. Before SAN ablation, the heart rate was 166.8?±?5.4?beats min(-1). Ablation of the SAN was clearly indicated by a sudden and significant decrease of heart rate to 108.6?±?9.6?beats min(-1) (P?
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