OBJECTIVE Certain gut peptides exert gastroprotective effects. However, the underlying mechanism is not fully understood. This study examines the contribution of afferent neurons, calcitonin gene-related peptide, and nitric oxide to the protection conferred by gastrin 17 in the rat stomach. METHODS Gastroprotection by gastrin 17 against ethanol-induced gross and histological damage was studied after capsaicin-induced defunctionalization of afferent neurons, pretreatment with the calcitonin gene-related peptide receptor antagonist human calcitonin gene-related peptide8-37, anti-calcitonin gene-related peptide antibodies, and the NO synthase inhibitor NG-nitro-L-arginine. RESULTS Gastrin 17 (1-25 pmol/kg) dose-dependently prevented mucosal damage caused by ethanol. Protection was inhibited by functional ablation of afferent neurons or pretreatment with human calcitonin gene-related peptide8-37 (50% inhibitory dose, 86 pmol.kg-1.min-1), anticalcitonin gene-related peptide antibodies, or NG-nitro-L-arginine (50% inhibitory dose, 1 mg/kg). L-Arginine but not D-arginine reversed the effect of NG-nitro-L-arginine. Effects on gross damage were paralleled by histology. Protective doses of gastrin 17 increased gastric mucosal blood flow and, in addition, elevated plasma gastrin concentrations to the same extent as intragastric peptone perfusion. CONCLUSIONS Gastrin 17 has potent gastroprotective activity that involves afferent neurons, calcitonin gene-related peptide, and NO.