[Effects of purinergic analogues on spontaneous contraction and electrical activities of gastric antral circular muscle in guinea-pig].
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 by using intracellular microelectrode. Electrical and mechanical activities were recorded by chart recorder. ATP and 2-MeSATP potentiated the mechanical activity but did not affect electrical activity in gastric circular smooth muscle. ATP and 2-MeSATP-induced contraction was effectively blocked by nonselective P2y-purinoceptor antagonist, reactive-blue-2 and suramin, but ATP-induced contraction was not blocked by alpha,beta-MeATP-induced desensitization of P2x-purinoceptors. However, alpha,beta-MeATP, P2x-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 P2x-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 block ATP-induced contraction. The results suggest that: (1) ATP- and analogues-induced contraction is mediated by P2y-purinoceptor, whereas alpha,beta-MeATP-induced relaxation by P2x-purinoceptor in guinea-pig gastric antral circular smooth muscle. (2) ATP-induced contraction is dependent on extracellular calcium, but Ca2+ entry is not mediated by L-type calcium channel. (3) Prostaglandins are not involved in ATP- and analogue-induced contraction of gastric circular smooth muscle in guinea-pigs, and alpha,beta-MeATP-induced relaxation is related to membrane hyperpolarization.
Jin
Zheng
Z
Department of Physiology, Medical School, Shanghai Jiao Tong University, Shanghai 200030, China.
Guo
Hui-Shu
HS
Xu
Dong-Yuan
DY
Hong
Ming-Yu
MY
Li
Xiang-Lan
XL
Xu
Wen-Xie
WX
D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology*; D000818:Animals; D004594:Electrophysiology; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008839:Microelectrodes; D009119:Muscle Contraction / Q000187:drug effects* / Q000502:physiology; D009130:Muscle, Smooth / Q000187:drug effects* / Q000502:physiology; D058913:Purinergic Agonists; D011706:Pyloric Antrum / Q000187:drug effects / Q000502:physiology; D013873:Thionucleotides / Q000494:pharmacology
D058913:Purinergic Agonists; D013873:Thionucleotides; D000255:Adenosine Triphosphate; C008501:2-methylthio-ATP