The atypical antidepressant and neurorestorative agent tianeptine is a μ-opioid receptor agonist

摘要

Current pharmacological treatments of depression and related disorders suffer from major problems, such as a low rate of response, slow onset of therapeutic effects, loss of efficacy over time and serious side effects. Therefore, there is an urgent need to explore new therapeutic approaches that address these issues. Interestingly, the atypical antidepressant tianeptine already meets in part these clinical goals. However, in spite of three decades of basic and clinical investigations, the molecular target of tianeptine, as well as its mechanism of action, remains elusive. Herein, we report the characterization of tianeptine as a μ-opioid receptor (MOR) agonist. Using radioligand binding and cell-based functional assays, including bioluminescence resonance energy transfer-based assays for G-protein activation and cAMP accumulation, we identified tianeptine as an efficacious MOR agonist (K i Human of 383±183?nM and EC 50 Human of 194±70 nM and EC 50 Mouse of 641±120?nM for G-protein activation). Tianeptine was also a full δ-opioid receptor (DOR) agonist, although with much lower potency (EC 50 Human of 37.4±11.2 μM and EC 50 Mouse of 14.5±6.6 μM for G-protein activation). In contrast, tianeptine was inactive at the κ-opioid receptor (KOR, both human and rat). On the basis of these pharmacological data, we propose that activation of MOR (or dual activation of MOR and DOR) could be the initial molecular event responsible for triggering many of the known acute and chronic effects of this agent, including its antidepressant and anxiolytic actions.