Nitric oxide is involved in the non-adrenergic, non-cholinergic inhibitory neurotransmission of the pig intravesical ureter

NADPH-diaphorase histochemical staining and electrical field stimulation (EFS) were performed in vitro to investigate whether nitric oxide (NO) is involved in non-adrenergic non-cholinergic (NANC) inhibitory neurotransmission of pig intravesical ureter. NADPH-diaphorase activity was expressed in nerve trunks and thin nerve fibres around arteries and muscular bundles in the intravesical ureter. Relaxations to EFS were tetrodotoxin (10 −6 M)-sensitive which indicates their neurogenic origin. Addition of the NO-synthase inhibitor, l- N G-nitroarginine (L-NOARG, 3 × 10 −5 M), abolished the electrically induced relaxations, which were significantly reversed by l-arginine (3 × 10 −3 M). Addition of acidified sodium nitrite (NaNO 2, 10 −5−10 −3 M) evoked concentration-dependent relaxations of ureteral strips which were unaffected by L-NOARG. It is concluded that NO synthase is present in nerve fibres and NO seems to mediate the inhibitory neurotransmission of the porcine intravesical ureter.