HTR1A and major depressive disorder: In addition, enhanced 5-HT1A autoreceptor function has been associated with reduced serotonergic neurotransmission (as a lower baseline firing rate of DRN 5-HT neurons) in several models of depression [39], [57] and a significant negative correlation between serotonin synthesis and 5-HT1A binding potential has been reported in healthy volunteers [58].