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Effects of diazepam on the action potential and contractility of rabbit papillary muscle

Han Xinqiang, Tang Shuben, Zhang Haiyan

Department of Physiology, Henan Medical University. Zhengzhou, China

Abstract

Effects of diazepam, verapamil and PK11195 on the action potential and contractility of the rabbit papillary muscle were investigated. Some comparisons were also made between the effects of diazepam on the contractility of the rabbit and the guinea pig. 0.7-22.4×10~(-6)mol/L diazapem shortened the duration of the action potential,(APD) and calcium-dependent action potential (Ca-AP), and decreased the maximum rise rate as well as the amplitude of the Ca-AP in the rabbit papillary muscle, which was accompanied by a decrease of contractility. The effect of diazepam on the contractility was more pronounced in the guinea pig. 2×10~(-6)mol/L verapamil suppressed the Ca-AP of the rabbit papillary muscle, an effect that.could be antagonized by increasing the external calcium concentration. The curve relating APD or contractility to diazepam dosage could be shifted to the right by 1×10~(-6) mol/L PKI 1195. In the presence of PK11195, the Ca-AP was.more resistant to the effect of verapamil. Our experimental results suggest: (a) Benzodiazepine binding sites in the rabbit papillary muscle may act as peripheral benzodiazepine receptors; (b) Activation of these receptors can result in a decrease of calcium influx; (c) Species differences may exist in the density and responsibility of this receptor.

Key words: Rabbit papillary muscle;Benzodiazepine receptor;Dizzepam;PK11195

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Citing This Article：

Han Xinqiang, Tang Shuben, Zhang Haiyan. Effects of diazepam on the action potential and contractility of rabbit papillary muscle. Acta Physiol Sin 1987; 39 (4): (in Chinese with English abstract).