Possible Roles of Nitric Oxide and Vasoactive Intestinal Polypeptide on Relaxation Induced by Isoprenaline in Isolated Muscle Strips of the Mouse Gastric Fundus

The possible role of nitric oxide (NO) and vasoactive intestinal polypeptide on isoprenaline-induced relaxation of the mouse longitudinal gastric fundal strips precontracted with 5.4 x 10(-7) M carbachol was investigated. Isoprenaline (5 x 10(-7) M, 10(-6) M and 5 x 10(-6) M) produced a concentration-dependent relaxations. NG-nitro L-arginine (10(-4) M) partly inhibited isoprenaline-induced relaxation. The inhibitory action of NG-nitro L-arginine was reversed by 4 x 10(-4) M L-arginine but not by 4 x 10(-4) M D-arginine. NG-nitro L-arginine (10(-4) M) did not affect the relaxation caused by sodium nitroprusside (10(-6) M). Vasoactive intestinal polypeptide antibody 7913 (1:160 dilution) partly inhibited isoprenaline-induced relaxation. This inhibition was greater on the response to the higher isoprenaline concentration (5 x 10(-6) M) than to the lower concentration (10(-6) M). The combination of vasoactive intestinal polypeptide antibody and NG-nitro L-arginine significantly enhanced the inhibition on 10(-6) M isoprenaline action. These results suggest that nitric oxide and vasoactive intestinal polypeptide may partly contribute to the relaxation induced by isoprenaline in the mouse gastric fundus precontracted with carbachol.