HTR1A and major depressive disorder: The properties of buspirone as a full agonist of presynaptic and partial agonist of postsynaptic 5-HT1A receptors determine its use in combination with other antidepressants to increase efficacy and reduce side effects in the treatment of depression (Albert and François, 2010; Albert and Fiori, 2014; Stuivenga et al., 2019).