This study was designed to determine the possible potentiation of catalepsy behavior after coadministration of N(G)-nitro-L-arginine (L-NOARG), an inhibitor of nitric oxide synthase (NOS), and tiapride, a specific antagonist for D2 receptors, in male mice. Catalepsy was measured by the bar test. Two successive evaluations were carried out 60 and 90 min after injections. The induction of catalepsy following coadministration of L-NOARG (25 and 50 mg/kg) and tiapride (200 mg/kg) was significantly higher than the sum of catalepsy scores after administration of L-NOARG and tiapride separately. Coadministration of L-NOARG and tiapride produced a clear potentiation of their effects on catalepsy in mice. These results underline the view that nitric oxide (NO) interacts with central dopamine D2 transmission.