The functional role of non-adrenergic non-cholinergic (NANC) nerves in the autonomic control of the male mini-pig bladder neck was investigated in the present study. Electrical stimulation of muscle strips from male mini-pig bladder neck showed biphasic response with initial phasic contraction followed by post-contractile relaxation. Electrical stimulation in the presence of four autonomic blockers (atropine 10-6 M, propanolol 10-6 M, phentolamine 10-6 M and guanethidine 10-6 M) showed suppression of 68 ± 15% of the contractile response (P < 0.05, n = 8) but no significant change in the relaxation response. Alpha-chymotrypsin 2 U/ml, L-N(G)-monomethyl-L-arginine acetate (a nitric oxide synthetase inhibitor) 10-4 M, 8-phenylthiophylline (a P1-purinoceptor antagonist) 10-6 M, and pyridoxal-phosphate-6-azophenyl-2',4'-disulphoric acid tetrasodium salt (a P(2Y)-purinoceptor antagonist) 3 x 10-5 M did not alter the NANC response significantly. On the other hand, reactive blue-2 (a P(2Y)-purinoceptor antagonist) 3 x 10-5 significantly reduced the relaxation by 79 ± 9%. The result suggested that the P(2Y)-purinoceptor is involved in the electrically induced NANC post-contractile relaxation of the mini-pig bladder neck smooth muscle.
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