Complex sentence: Tianeptine is a selective serotonin reuptake enhancer (SSRE), opposite to the action of SSRIs, although other possible mechanisms may underpin its antidepressant effects.
Split into simpler sentences: Tianeptine is a selective serotonin reuptake enhancer (SSRE), opposite to the action of SSRIs. Although other possible mechanisms may underpin its antidepressant effects.