EVIDENCE OF P-2Y-PURINOCEPTOR MEDIATED BLADDER NECK SMOOTH-MUSCLE POST-CONTRACTILE RELAXATION IN THE MALE MINIPIG

The functional role of non-adrenergic non-cholinergic (NANC) nerves in the autonomic control of the male mini-pig bladder neck was investiga ted in the present study. Electrical stimulation of muscle strips from male mini-pig bladder neck showed biphasic response with initial phas ic contraction followed by post-contractile relaxation. Electrical sti mulation 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-NG-monomethyl-L-arginine acetate (a nitric oxi de synthetase inhibitor) 10(-4) M, 8-phenylthlophylline (a P-1-purinoc eptor 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) sign ificantly reduced the relaxation by 79 +/- 9%. The result suggested th at the P-2Y-purinoceptor is involved in the electrically induced NANC post-contractile relaxation of the mini-pig bladder neck smooth muscle . (C) 1997 Elsevier Science Ireland Ltd.