Background: Nitric oxide (NO) is a neuromodulator and an intercellular and retrograde messenger that mediates several functions in the central nervous system. The effects of ethanol (EtOH) on neuronal NO-dependent pathways have been the focus of recent research. Most studies have concentrated on the actions of chronic EtOH exposure. In this study, we examined the role of NO-dependent pathways in the acute actions of EtOH. Methods: We used the elevated plus-maze test to study the role of NO-dependent pathways in the behavior of rats treated with acutc EtOH. We tested the effects of 7-nitroindazole, a reversible competitive inhibitor of nitric oxide synthasc. We also studicd the effects of the cyclic guanylate monophosphate (cGMP) analog, 8-Bromoguanosine cyclic 3′, 5′-monophosphate sodium salt, and the NO donors S-nitroso-N-acetylpenicillamine or sodium nitroprusside. Results: When injected by either intraperitoneal (6 mg/kg) or intrahippocampal (20 nmol) routes, 7-nitroindazole increased the percentage of open arm entries and time spent in open arms for rats injected with EtOH (1.0 g/kg, ip). This dose of EtOH did not produce an anxiolytic effect when administered alone. Additional experiments were performed with a dose of 1.2 g/kg of EtOH (ip), which produced an anxiolytic effcct. Intrahippocampal administration of the cGMP analog, 8-Bromoguanosine cyclic 3′3′-monophosphate sodium salt (40 nmol), or the NO donors S-nitroso-N-acetylpenicillamine (20 or 40 nmol) or sodium nitroprusside (20 or 40 nmol) blocked the anxiolytic effect of this dose of EtOH. Conclusions: These results indicate that inhibition of NO-dependent pathways enhances, whereas stimulation of these pathways decreases, the efficacy of EtOH to produce anxiolytic effects in rats. We postulate that NO-dependent increases in guanylate cyclase activity and cGMP levels oppose the anxiolytic effects produced by acute EtOH administration.