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ACh--evoked membrane hyperpolarization in smooth muscle cells of rat vas deferens {sl in vitro}： Involvement of K~(+) channels and NO

Fan Ping, Li Li, Liu Zhengjiang, Si Junqiang, Zhang Zhiqin, Zhao Lei, Ma Ketao

Laboratory of Xinjiang Endemic and Ethnic Diseases, Institute of Electrophysiology, Medical College Shihezi University.Shihezi 832002,Xinjiang

Abstract

To explore the underlying mechanism of acetylcholine （ACh）-evoked membrane hyperpolarizing response in isolated rat vas deferens smooth muscle cells （SMCs）, intracellular microelectrode recording technique and intracellular microelectrophoresis fluorescent staining technique were used to study ACh-evoked membrane hyperpolarizing response in SMCs freshly isolated from Wistar rat vas deferens. By using microelectrodes containing fluorescent dye 0.1% propidium iodide （PI）, 37 and 17 cells were identified as SMCs in outer longitudinal and inner circular muscular layers, respectively. The resting membrane potentials of SMCs were （-53.56±3.88） mV and （-51.62±4.27） mV, respectively. The membrane input resistances were （2245.60±372.50） M#OMEGA# and （2101.50±513.50）M#OMEGA#, respectively. ACh evoked membrane hyperpolarizing response in a concentration-dependent manner with an EC_(50) of 36 #mu#mol/L. This action of ACh was abolished by both a non-sepeific muscarinic （M） receptor antagonist atropine （1 #mu#mol/L） and a selective M_(3) receptor antagonist diphenylacetoxy-N-methylpiperidine-methiodide （DAMP, 100 nmol/L）. ACh-evoked membrane hyperpolarization was also abolished by a nitric oxide synthase inhibitor N-nitro-L-arginine methyl ester （L-NAME, 300 #mu#mol/ L） and suppressed by an ATP-sensitive potassium （K_(ATP)） channel blocker glipizide （5 #mu#mol/L） and an inward rectifier potassium （K_(ir)） channel inhibitor bariumion （50 #mu#mol/L）. A combination of glipizide and bariumion abolished ACh-evoked membrane hyperpolarizing response. The results suggest that ACh-evoked membrane hyperpolarization in rat vas deferens SMCs is mediated by M_(3) receptor followed with activation of K_(ATP) channels, K_(ir) channels, and NO release.

Key words: vas deferens;Smooth muscle cell;hyperpolarization;Potassium channel;Acetylcholine

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Citing This Article：

Fan Ping, Li Li, Liu Zhengjiang, Si Junqiang, Zhang Zhiqin, Zhao Lei, Ma Ketao. ACh--evoked membrane hyperpolarization in smooth muscle cells of rat vas deferens {sl in vitro}： Involvement of K~(+) channels and NO. Acta Physiol Sin 2007; 59 (3): 331-338 (in Chinese with English abstract).