POSSIBLE ROLES OF NITRIC-OXIDE AND VASOACTIVE INTESTINAL POLYPEPTIDE ON RELAXATION INDUCED BY ISOPRENALINE IN ISOLATED MUSCLE STRIPS OF THEMOUSE GASTRIC FUNDUS

The possible role of nitric oxide (NO) and vasoactive intestinal polyp eptide on isoprenaline-induced relaxation of the mouse longitudinal ga stric fundal strips precontracted with 5.4 X 10(-7)M carbachol was inv estigated. Isoprenaline (5 X 10(-7)M, 10(-6)M and 5 X 10(-6)M) produce d a concentration-dependent relaxations. N-G-nitro L-arginine (10(-4)M ) partly inhibited isoprenaline-induced relaxation. The inhibitory act ion of N-G-nitro L-arginine was reversed by 4 X 10(-4)M L-arginine but not by 4 X 10(-4)M D-arginine. N-G-nitro L-arginine (10(-4)M) did not affect the relaxation caused by sodium nitroprusside (10(-6)M). Vasoa ctive intestinal polypeptide antibody 7913 (1:160 dilution) partly inh ibited isoprenaline-induced relaxation, This inhibition was greater on the response to the higher isoprenaline concentration (5 X 10(-6)M) t han to the lower concentration (10(-6)M). The combination of vasoactiv e intestinal polypeptide antibody and N-G-nitro L-arginine significant ly enhanced the inhibition on 10(-6)M isoprenaline action. These resul ts suggest that nitric oxide and vasoactive intestinal polypeptide may partly contribute to the relaxation induced by isoprenaline in the mo use gastric fundus precontracted with carbachol.