Dopaminergic effects of buspirone, a novel anxiolytic agent

The novel anxiolytic drug buspirone raised striatal levels of the dopamine metabolites homovanillic acid (HVA) and dihydroxyphenylacetic acid (DOPAC) 1 hr after oral administration. This effect was dose-dependent with a peak at 60 min. No changes were observed in the levels of 3-methoxytyramine (3MT), the extraneuronal metabolite of dopamine. Noradrenaline, serotonin and its metabolite 5-hydroxyindoleacetic acid (5HIAA) were not affected. Buspirone displaced [3H]spiroperidol from striatal binding sites, with an IC50 (1.8 x 10(-7) M), comparable to that of clozapine (IC50 = 1.4 x 10(-7) M) but considerably lower than that of haloperidol (4.7 x 10(-9) M). Buspirone was only a weak inhibitor of dopamine-stimulated adenyl cyclase. Buspirone was not active on the binding of trifluoperazine to calmodulin and did not modify calmodulin-induced activation of phosphodiesterase (PDE). Repeated administration of buspirone did not increase the number of DA receptors. These data show that, although buspirone has antidopaminergic activity, it can hardly be classified as a classic neuroleptic agent.