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To characterize non-adrenergic non-cholinegic(NANC) nerve mediated contractile responses in circular smooth muscle of bovine reticular groove, we investigated NANC relaxation and contraction induced by electric field stimulation to enteric nerves. In the presence of atropine(1μM) and guanethidine(50μM), electric field stimulation at frequency of 1 to 16㎐(square pulses, 0.5㎳ duration, 70V) evoked clear-cut relaxations through stimulations. Transient ´rebound contraction´ was occured when the stimulus was switched off. All of the responses (relaxation and rebound contraction) were dose-dependently blocked by Nw-nitro-_L- arginine methyl ester(LNAME), an inhibitor of nitric oxide synthesis, and methylene blue, and inhibitor of soluble guanylate cyclase. Tetraethyl ammonium(TEA), a potassium channel blocker, did not block the NANC relaxations.
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