The antidepressanttianeptine was once claimed to be a (selective) serotonin reuptake enhancer (SRE or SSRE), but the role of serotonin reuptake in its mechanism is doubtful. Tianeptine has no affinity to the serotonin transporter, neither increases nor decreases extracellular levels of serotonin in cortico-limbic structures of conscious rats, and it didn't show any other long-term effect on the serotonin pathway. Thus, tianeptine's role as an SSRE may have been the coincidence of a yet unknown mechanism of action.