Chronic SSRI treatment is known to produce not only desensitization of 5-HT-1A autoreceptors but also changes in postsynaptic 5-HT-1A serotonin receptor function [157, 158] and involvement of 5-HT-1A receptors localized in the paraventricular nucleus of the hypothalamus (PVN) in anxiety and depression is suggested [35, 159]. Here, HTR1A is linked to major depressive disorder.