Nitric oxide (NO) has been implicated in alcohol drinking behavior using NO synthase (NOS) inhibitors that are nonselective of the different isoforms of NOS. In the brain, there are two constitutive isoforms of NOS, neuronal NOS (nNOS) and endothelial NOS (eNOS). We used an antisense oligodeoxynucleotide directed against nNOS in ethanol dependent male Wistar rats to examine the specific contribution of nNOS in the control of ethanol intake. Rats were subjected to a free-choice situation water/ethanol (10% v/v) after chronic ethanol intoxication by inhalation of ethanol vapor. During the free-choice situation, rats were twice daily for 4 days intracerebroventricularly injected with either saline, or end-capped phosphorothioate-protected antisense or mismatch oligodeoxynucleotide (25 microg/4 microl per injection), or acamprosate (1 mg/kg body weight) as reference product for its anticraving properties. Our results showed that the antisense treatment, but not the mismatch treatment, reduced both ethanol intake and ethanol preference during treatment and posttreatment periods (by 25-30%) without alteration of the body weight gain. The antisense treatment, but not the mismatch treatment, also down-regulated nNOS mRNA levels (by 30%) and NOS activity in the hippocampus. The anticraving drug, acamprosate reduced both ethanol intake (by 58%) and ethanol preference. All these results suggest that nNOS is involved in the regulation of alcohol dependence.