首页|Opiate-induced constipation related to activation of small intestine opioid μ2-receptors

Opiate-induced constipation related to activation of small intestine opioid μ2-receptors

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AIM:To investigate the role of opioid μ-receptor subtype in opiate-induced constipation (OIC).METHODS:The effect of loperamide on intestinal transit was investigated in mice.Ileum strips were isolated from 12-wk-old male BALB/c mice for identification of isometric tension.The ileum strips were precontracted with 1 μmol/L acetylcholine (ACh).Then,decrease in muscle tone (relaxation) was characterized after cumulative administration of 0.1-10 μmol/k loperamide into the organ bath,for a concentration-dependent study.Specific blockers or antagonists were used for pretreatment to compare the changes in loperamide-induced relaxation.RESULTS:In addition to the delay in intestinal transit,loperamide produced a marked relaxation in isolated ileum precontracted with ACh,in a dose-dependent manner.This relaxation was abolished by cyprodime,a selective opioid μ-receptor antagonist,but not modified by naloxonazine at a dose sufficient to block opioid μ-1 receptors.Also,treatment with opioid μ-1 receptor agonist failed to modify the muscle tone.Moreover,the relaxation by loperamide was attenuated by glibenclamide at a dose sufficient to block ATP-sensitive K+ (KATP) channels,and by protein kinase A (PKA) inhibitor,but was enhanced by an inhibitor of phosphodiesterase for cyclic adenosine monophosphate (cAMP).CONCLUSION:Loperamide induces intestinal relaxation by activation of opioid μ-2 receptors via the cAMPPKA pathway to open KATP channels,relates to OIC.

ATP-sensitive K+ channelsIsometric tensionLoperamideOpioid μ-receptorsSmall intestine

Wency Chen、Hsien-Hui Chung、Juei-Tang Cheng

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Department of Internal Medicine, E-Da Hospital and I-Shou University, Kaohsiung City, Taiwan 82401, China

Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan City, Taiwan 70101, China

Institute of Medical Sciences, Chang Jung Christian University, Quei-Jen, Tainan City, Taiwan 71101, China

2012

10.3748/wjg.v18.i12.1391

世界胃肠病学杂志(英文版)
太原消化病研治中心

世界胃肠病学杂志(英文版)

SCI
影响因子：1.001
ISSN：1007-9327
年,卷(期)：2012.18(12)
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