The serotonin 1A receptor (5-HT) is expressed presynaptically on raphe neurons and works as an inhibitory autoreceptor. It is also expressed postsynaptically in limbic and cortical areas involved in mood and emotional regulation. Alteration in expression and function of 5-HT 1A receptors is believed play an important role in etiopathology and treatment of mood disorders such as major depression. Here in this book we reviewed transcriptional regulation of 5-HT1A receptor gene and introduced a novel regulator which acts on expression of 5-HT1A receptor postsynaptically.