HTR1A encodes the 5-hydroxytryptamine receptor 1A, a G-protein coupled receptor that binds serotonin and mediates inhibitory neurotransmission 1. The receptor couples to Gi/Go proteins, inhibiting adenylyl cyclase activity and activating phosphatidylinositol-calcium signaling pathways that regulate intracellular calcium release 1. HTR1A plays crucial roles in regulating serotonin and dopamine metabolism, affecting neural activity, mood, and behavior 2. The gene shows significant clinical relevance across multiple disorders. Genetic polymorphisms, particularly rs6295, have been associated with suicidal behavior risk, though meta-analyses show conflicting results 34. HTR1A variants also influence treatment response to antipsychotics with 5-HT1A partial agonism in schizophrenia patients 5. Expression studies reveal altered HTR1A levels in autism spectrum disorders, with the gene showing undetectable expression in ASD samples compared to controls 6. Additionally, HTR1A contributes to portal hypertension by mediating portal vein smooth muscle contraction, suggesting therapeutic potential for liver disease complications 7. The receptor's diverse functions highlight its importance in neuropsychiatric disorders and vascular pathophysiology.