['We showed previously that the acute effect of ethanol on intestinal immunoglobulin A (IgA) expression might be mediated by endogenous nitric oxide (NO). To extend these findings, this study was designed to investigate a possible role of neuronal NO synthase (nNOS) in the observed phenomenon, using 7-nitroindazole (7-NI), a selective inhibitor of its activity.', 'Adult male Wistar rats were treated with: (a) ethanol (4\xa0g/kg, intraperitoneally, i.p.), (b) 7-NI (25\xa0mg/kg, i.p.) followed by ethanol (4\xa0g/kg, i.p.) 30\xa0min later and (c) 7-NI (25\xa0mg/kg, i.p.) followed by saline 30\xa0min later. Untreated rats were used as controls. The concentrations of serum and intestinal IgA were measured by enzyme-linked immunosorbent assay, while the expression of nNOS was determined using western blot and immunohistochemistry.', 'Acute ethanol treatment significantly increased the concentration of IgA in the ileal extracts, whereas it decreased its serum level. Inhibition of nNOS activity by 7-NI abolished this action of alcohol on IgA. Additionally, western blot analysis revealed that the acute alcohol administration induced an increase in the expression of intestinal nNOS. Furthermore, nNOS-immunoreactive cells, observed within the lamina propria of small intestine, were numerous in ethanol-treated rats.'] Does neuronal nitric oxide synthase mediate the effect of ethanol on IgA?