Researchers find a new target for antidepressants

May 15 (UPI) -- Researchers at Columbia University Medical Center found the brain's mu opioid receptors are responsible for the depression-relieving effects of tianeptine.

Tianeptine is an antidepressant also used to relieve pain without causing withdrawal symptoms, has approved for use in Europe, Asia and South America. The drug works as well as selective serotonin reuptake inhibitors, or SSRIs, but little was known about exactly how tianeptine worked to alleviate depression symptoms.

The researchers' findings, detailed in a study published in Neuropsychopharmacology, that tianeptine fails to produce an antidepressant effect in mice when the mu opioid receptor is blocked with antagonists or genetically removed. A metabolite of tianeptine known as MCS, is the drug's active ingredient and may be used to create more effective versions of the antidepressant because, currently, medication adherence is low and patients need to take three doses a day.

Morphine is the best known agonist of the mu opioid receptor, however, morphine is often abused because it is an effective pain reliever. Researchers found that tianeptine also reduces pain but does not cause tolerance or withdrawal symptoms like morphine.

"Our work highlights a novel way to provide antidepressant treatment and provides a new avenue for the development of potentially more effective antidepressants that offer relief to patients who do not respond to current treatments," Rene Hen, professor of neuroscience and pharmacology at Columbia University, said in a press release.