IS NITRIC-OXIDE INVOLVED IN 5-HT2B RECEPTOR-MEDIATED CONTRACTION IN THE RAT STOMACH FUNDUS

Although contraction of the rat stomach fundus by 5-HT is known to be mediated by the 5-HT2B receptor, the second messenger pathways involve d in this response remain unclear. Since nitric oxide (NO) has been as sociated with contraction of certain gastrointestinal smooth muscle, t he purpose of this study was to determine if NO is involved in 5-HT-in duced contraction in the rat stomach fundus. The arginine analogs L-NA ME and L-NMMA, at a concentration (100 mu M) established to inhibit NO synthase in the rat stomach fundus by inhibiting depolarization-induc ed relaxation in this tissue, had no effect on 5-HT contraction. Furth ermore, the NO donors sodium nitroprusside and SNAP did not contract r at stomach fundus under basal tone, whereas 5-HT was a potent contract ile agonist. These data do not support a role for NO in 5-HT2B recepto r-mediated contraction in the rat stomach fundus.