The antidopaminergic action of S-20098 is mediated by benzodiazepine/GABAA receptors in the striatum

The naphthalenic compound S-20098, which is a melatonergic agonist, inhibits [3H]diazepam binding in striatal membranes. S-20098 also inhibits apomorphine-induced turning in 6-hydroxydopamine lesioned rats. This antidopaminergic effect is blocked by either intraperitoneal injection of the central-type benzodiazepine (BZ) antagonist, flumazenil, or intrastriatal injection of the GABA(A) antagonist, bicuculline. These findings indicate that S-20098 can activate central-type BZ receptors, and its antidopaminergic action, like that of melatonin, involves a GABAergic mechanism in the striatum.