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KMID : 0811720090130050393
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Korean Journal of Physiology & Pharmacology
2009 Volume.13 No. 5 p.393 ~ p.400
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The Influences of G Proteins, Ca2＋, and K＋ Channels on Electrical Field Stimulation in Cat Esophageal Smooth Muscle
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Park Jun-Hong
Kim Hyun-Sik
Park Sun-Young
Im Chae-Uk
Jeong Ji-Hoon
Kim In-Kyeom
Sohn Uy-Dong
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Abstract
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NO released by myenteric neurons controls the off contraction induced by electrical field stimulation (EFS) in distal esophageal smooth muscle, but in the presence of nitric oxide synthase (NOS) inhibitor, L-NAME, contraction by EFS occurs at the same time. The authors investigated the intracellular signaling pathways related with G protein and ionic channel EFS-induced contraction using cat esophageal muscles. EFS-induced contractions were significantly suppressed by tetrodotoxin (1?M) and atropine (1?M). Furthermore, nimodipine inhibited both on and off contractions by EFS in a concentration dependent meaner. The characteristics of ’on’ and ’off’ contraction and the effects of G-proteins, phospholipase, and K＋ channel on EFS-induced contraction in smooth muscle were also investigated. Pertussis toxin (PTX, a Gi inactivator) attenuated both EFS-induced contractions. Cholera toxin (CTX, Gs inactivator) also decreased the amplitudes of EFS-induced off and on contractions. However, phospholipase inhibitors did not affect these contractions. Pinacidil (a K＋ channel opener) decreased these contractions, and tetraethylammonium (TEA, K＋Ca channel blocker) increased them. These results suggest that EFS-induced on and off contractions can be mediated by the activations Gi or Gs proteins, and that L-type Ca2＋ channel may be activated by G-protein ? subunits. Furthermore, K＋Ca- channel involve in the depolarization of esophageal smooth muscle. Further studies are required to characterize the physiological regulation of Ca2＋ channel and to investigate the effects of other K＋ channels on EFS-induced on and off contractions.
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KEYWORD
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EFS, Cat esophageal, Circular smooth muscle, NO, L-type Ca2＋ channel
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