Influence of α‐chymotrypsin and trypsin on the non‐adrenergic non‐cholinergic relaxation in the rat gastric fundus

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Abstract
1 Relaxations of the rat gastric fundus were induced by electrical stimulation of the non-adrenergic non-cholinergic (NANC) neurones, by vasoactive intestinal polypeptide (VIP), by noradrenaline and by isopropylnoradrenaline. The influence of α-chymotrypsin and trypsin thereupon was studied. 2 α-Chymotrypsin 2 u ml−1, present for 30 min, antagonized completely the VIP-induced relaxation, but not the stimulation-induced relaxation; α-chymotrypsin 10 u ml−1 also partially antagonized the stimulation-induced relaxation. When α-chymotrypsin 2 u ml−1 was added after the relaxation had occurred, it antagonized completely the VIP-induced relaxation, but it also partially antagonized the stimulation-induced relaxation. The partial antagonism of the stimulation-induced relaxation was more pronounced with α-chymotrypsin 10 u ml−1. 3 Trypsin, 10−6 m and 3 × 10−6 m, had effects on VIP-and stimulation-induced relaxations similar to those of α-chymotrypsin. 4 The relaxations induced by noradrenaline and isopropylnoradrenaline were not influenced by α-chymotrypsin or trypsin, respectively. 5 The results suggest that a peptide, possibly VIP, is involved in the NANC relaxation of the rat gastric fundus.