Nitrergic and peptidergic components of NANC relaxations of cat gastric fundus

The mediators of non-adrenergic non-cholinergic (NANC) relaxation of cat gastric fundus were examined in vitro. Electrical field stimulation (EFS, 10 pulses train and 10 s train) induced tetrodotoxin (TTX) sensitive relaxations in the presence of atropine and guanethidine. Relaxation induced by vasoactive intestinal polypeptide (VIP) was abolished by alpha-chymotrypsin (alpha-CT). N omega-nitro-L-arginine (L-NNA) completely inhibited relaxation induced by EFS of 10 pulses train at all frequencies. L-NNA completely inhibited the relaxation induced by EFS of 10 s train at low frequencies but partly that at high frequencies; alpha-CT had an additive to L-NNA inhibitory effect on the relaxation. The results suggest a nitrergic nature of NANC relaxation in cat gastric fundus upon EFS of 10 pulses, and a nitrergic and peptidergic (VIP) nature of relaxations upon EFS of 10 s train.