Tofisopam, a 2,3-benzodiazepine, has been shown to have anxiolytic activity. However, in contrast to the widely used 1,4-benzodiazepines, it has no anticonvulsant, sedative or muscle relaxant effects. Tofisopam enhanced the behavioural actions of various dopaminergic drugs, both direct agonists, such as apomorphine (climbing behaviour in mice), and indirect agonists, such as (+)-amphetamine and amineptine (jumping behaviour in mice). Chronic treatment with lithium abolished the tofisopam-induced increase in the activity of these dopaminergic drugs. Thus tofisopam appears to induce acutely an increase in the sensitivity of central dopaminergic receptors which can be prevented by pretreatment with lithium.