ACh-evoked membrane hyperpolarization in smooth muscle cells of rat vas deferens in vitro: involvement of K(+) channels and NO.
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) MOmega and (2101.50+/-513.50) MOmega, respectively. ACh evoked membrane hyperpolarizing response in a concentration-dependent manner with an EC(50) of 36 micromol/L. This action of ACh was abolished by both a non-sepcific muscarinic (M) receptor antagonist atropine (1 mumol/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 micromol/L) and suppressed by an ATP-sensitive potassium (K(ATP)) channel blocker glipizide (5 micromol/L) and an inward rectifier potassium (K(ir)) channel inhibitor bariumion (50 micromol/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.
Fan
Pin
P
Laboratory of Xinjiang Endemic and Ethnic Diseases, Institute of Electrophysiology, Medical College Shihezi University, Shihezi 832002, China.
Li
Li
L
Liu
Zheng-Jiang
ZJ
Si
Jun-Qiang
JQ
Zhang
Zhi-Qin
ZQ
Zhao
Lei
L
Ma
Ke-Tao
KT
D000109:Acetylcholine / Q000494:pharmacology*; D000818:Animals; D005913:Glipizide / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D032389:Myocytes, Smooth Muscle / Q000502:physiology*; D009569:Nitric Oxide / Q000502:physiology*; D015221:Potassium Channels / Q000502:physiology*; D024661:Potassium Channels, Inwardly Rectifying; D051381:Rats; D017208:Rats, Wistar; D014649:Vas Deferens / Q000187:drug effects* / Q000502:physiology
D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; D009569:Nitric Oxide; D000109:Acetylcholine; D005913:Glipizide