Evidence for involvement of nitric oxide (NO) or a related nitroso-compound in NANC inhibitory neurotransmission in the pigeon oesophageal smooth muscle

1 In the pigeon oesophageal smooth muscle electrical field stimulation (EFS ), in the presence of atropine and guanethidine, evoked TTX-sensitive inhib itory effects on both the electrical and mechanical activity. 2 N-Omega-Nitro L-arginine (L-NA) 10.1-100 mu M), an inhibitor of nitric ox ide synthase, reduced the inhibitory EFS-evoked effects. 3 Sodium nitroprusside (SNP) (10 mu M), a NO-donor, mimicked the effects ev oked by EFS. 4 Apamin (1 mu M) perfusion did not modify the inhibitory effects induced b y SNP. 5 Cystamine (10 mu M), a guanylate-cyclase inhibitor, reduced the inhibitor y effects elicited by EFS. 6 This study shows a possible role for NO in the non-adrenergic non-choline rgic (NANC) inhibitory responses induced by EFS in the pigeon oesophagus.