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Effects of purinergic analogues on spontaneous contraction and electrical activities of gastric antral circular muscle in guinea--pig

Jin Zheng, Guo Huishu, Hong Mingyu, Li Xianglan, Xu Wenxie

Department of Physiology, Medical School, Shanghai Jiao Tong University.Shanghai 200030；China

Abstract

In order to investigate the role of non-adrenergic non-cholinergic nerves in regulating mechanical and electrical activity of gastric circular smooth muscle, the effects of ATP and its analogues on gastric motility and electrical activities were observed in guinea-pig. In organ bath system, isometric force of the circular smooth muscle of guinea-pig gastric antrum was measured. Electrical activity of the muscle was recorded using intracellular microelectrode. Electrical and mechanical activities were recorded by chart recorder. ATP and 2-MeSATP potentiated the mechanical activity but didn’t affect electrical activity in gastric circular smooth muscle. ATP and 2-MeSATP-induced contraction was effectively blocked by nonselective P_(2y)-purinoceptor antagonist, reactive-blue-2 and suramin, but ATP-induced contraction was not blocked by #alpha#,#beta#-MeATP-induced desensitization of P_(2x)-purinoceptors. However, #alpha#,#beta#-MeATP, P_(2x)-purinoceptor agonist, attenuated slow waves with membrane hyperpolarization and inhibited contraction. The relaxation by #beta#,#gamma#-MeATP was blocked by #alpha#,#beta#-MeATP-induced desensitization of P_(2x)-purinoceptors. ATP-induced contraction was blocked by external calcium-free, but not by nicardipine, a L-type calcium channel blocker. Indomethacin, a nonselective cyclooxygenase inhibitor, did not blocked ATP-induced contraction. The results suggest that: (1) ATP and analogues-induced contraction is mediated by P_(2y)-purinoceptor, whereas #alpha#,#beta#-MeATP-induced relaxation by P_(2x)-purinoceptor in guinea-pig gastric antral circular smooth muscle; (2) ATP-induced contraction is dependent on extracellular calcium, but Ca~(2+) entry is not mediated by L-type calcium channel; (3) Prostaglandins are not involved in ATP and its analogue-induced contraction of gastric circular smooth muscle in guinea-pigs; #alpha#,#beta#-MeATP-induced relaxation is related to membrane hyperpolarization.

Key words: ATP;P_(2Y)-purinoceptor;P_(2x)-purinoceptor;gastric circular smooth muscle

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Citing This Article：

Jin Zheng, Guo Huishu, Hong Mingyu, Li Xianglan, Xu Wenxie. Effects of purinergic analogues on spontaneous contraction and electrical activities of gastric antral circular muscle in guinea--pig. Acta Physiol Sin 2004; 56 (6): (in Chinese with English abstract).