Tianeptine is a new effective antidepressant drug. However, its neurochemical profile in animals differs from that of tricyclic or atypical antidepressants. In the present study, we compared the ex vivo effects of tianeptine on platelet serotonin uptake to those of clomipramine. Ex vivo, after subchronic (15 days, washout 24 h) treatment (10 mg/kg/day i.p.) in rats, tianeptine induced an increase (30%) in [14C]serotonin uptake at a [14C]serotonin concentration of 500 nM while clomipramine induced a decrease (40%) in [14C]serotonin uptake. Stimulation of uptake affected mainly Vmax but not Km. Tianeptine did not inhibit monoamine oxidase (MAO), MAOA or MAOB activity. In vitro, there was no binding of tianeptine to any of the various receptors examined: alpha- and beta-adrenergic, dopamine, serotonin, imipramine, GABA, glutamate, benzodiazepine, muscarinic, histamine, Ca2+ channels. After chronic administration (10 mg/kg/day for 15 days) tianeptine did not alter the concentration (Bmax) or the affinity (Kd) of alpha-2, beta-1, serotonin-1, serotonin-2, imipramine, benzodiazepine, or GABAB receptors. The major effect of tianeptine in rat platelets and synaptosomes is a small increase in 5-HT uptake after subchronic administration.