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 alpha-chymotrypsin and trypsin thereupon was studied. alpha-Chymotrypsin 2 u ml-1, present for 30 min, antagonized completely the VIP-induced relaxation, but not the stimulation-induced relaxation; alpha-chymotrypsin 10 u ml-1 also partially antagonized the stimulation-induced relaxation. When alpha-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 alpha-chymotrypsin 10 u ml-1. Trypsin, 10(-6) M and 3 X 10(-6) M, had effects on VIP- and stimulation-induced relaxations similar to those of alpha-chymotrypsin. The relaxations induced by noradrenaline and isopropylnoradrenaline were not influenced by alpha-chymotrypsin or trypsin, respectively. The results suggest that a peptide, possibly VIP, is involved in the NANC relaxation of the rat gastric fundus.
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Beurme et al. (1987) studied this question.
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