Despite its affinity to several serotonin receptors, such as the 5HT2B, 5-HT2C, 5HT5A, 5-HT1A, 5-HT1D, 5-HT1E, 5-HT6, and 5-HT7-receptors [34,35,36,37,38], the most important antidepressant mechanism of action is thought to be the (partial) agonism at the 5-HT2A receptor [11,39], relevant in the pathway implicated in suicidality and depression [40,41,42]. Here, HTR5A is linked to major depressive disorder.