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KMID : 0390119940340010147
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Journal of Pusan Medical College
1994 Volume.34 No. 1 p.147 ~ p.158
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Characterization of Non-adrenergic Non-cholinergic relaxation in the dog lower esophageal sphincter
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Abstract
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In this study, it was aimed to investigate the involvement of non-adrenrgic non-cholinergic (NANC) nerve fibers and the role of nitric oxide (NO) in the relaxation of dog lower esophageal sphincter(LES).
1. The changes in basal tone of isolated LES were observed for up to 2 hours during equilibration period. The resting tension was gradually increased throughout this period, as contrasted to the esophageal circular muscle strips.
2. Electrical field stimulatin (EFS) caused frequency-dependent relaxation of LES strips. The relaxation (100 μM). However, it was abolished under pretreatment with 1 μM tetrodotoxin.
3. NO synthase inhibitors.N-G-monomethyl-L-arginine (L-NMMA), NG-nitro-L-arginine methyl ester (L-NAME) and NG-nitro-L-arginine (L-NNA) caused reduction of EFS-induced relaxations in a dose-dependent manner these inhibitory effects of L-NMMA and
L-NNA
partially reversed by L-arginine (0.1mM), whereas that of L-NAME was little affected by L-arginine.
4. The changes in basal tone of LES strips were inconsistently increased upon application of NO synthase inhibitors.
5. Sodium nitroprusside (0.1-10μM) relaxed dose-dependently the tone of LES strips.
6. the relaxation elicited by EFS was significantly reduced by pretreatment with dexamethasone(2.5, 75 ad 250 μM for 20 min).
7. Cyclic GMP formation of the LES strips was elevated upon EFS(20 pps, 2 msec pulse duration at supramaximal voltage for 2 min) which was significant in comparison to basal level. After pretreatment with L-NNA (100μM)the increased c(GMP
formation was
partially reduced.)
Based on these results, it is concluded that the function of dog LES is controlled by the NANC nerves, an further, the relaxation is mediated by NO as an inhibitory neurotransmitter released from NANC nerve fibers.
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