HTR2A and depressive disorder: In another study, genes related to human major depression like serotonin receptor 2a gene (Htr2a), neurotrophic tyrosine kinase receptor type 2 and 3 genes (Ntrk2 and Ntrk3), corticotropin releasing hormone receptor 1 (Crhr1) and corticotropin releasing hormone (Crh) were differentially expressed in three animal models of depression: acute treatment with reserpine, olfactory bulbectomy and chronic treatment with corticosterone [9].