HTR1A and major depressive disorder: Investigation of the binding rate and activation of 5-HT2A, 5-HT1A, and SERT receptors in the auditory cortex of patients with MDD, compared to a control group, demonstrates that patients with MDD do not present changes in the binding rate of 5-HT1A and SERT receptors, but there is a significant reduction in the binding rate to the 5-HT2A receptor [77].