The Influences of G Proteins, Ca2+, and K+ Channels on Electrical Field Stimulation in Cat Esophageal Smooth Muscle
The Influences of G Proteins, Ca2+, and K+ Channels on Electrical Field Stimulation in Cat Esophageal Smooth Muscle
- 대한생리학회-대한약리학회
- The Korean Journal of Physiology & Pharmacology
- 제13권 제5호
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2009.01393 - 400 (8 pages)
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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 (1ՌM) and atropine (1ՌM). 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 Ձ 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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