HTR3C encodes the 5-hydroxytryptamine receptor 3C subunit, which forms serotonin-activated cation-selective ion channels that mediate fast depolarizing responses in neurons. The protein functions as part of heteromeric 5-HT3 receptor complexes localized to the plasma membrane, where it facilitates transmembrane transport of monoatomic cations and participates in synaptic neurotransmission 1. Genetically, HTR3C polymorphisms influence susceptibility to gastrointestinal and neuropsychiatric disorders. The rs6766410 allele A variant associates with decreased cyclic vomiting syndrome risk 2, while the rs489C>A polymorphism correlates with depressive and anxiety symptoms in irritable bowel syndrome patients 3. HTR3C variants have been identified in genome-wide association studies as risk loci for oesophageal adenocarcinoma specifically (rs9823696) 4 and migraine susceptibility 5. Clinically, HTR3C represents a potential biomarker for Alzheimer's disease among five key neurotransmitter receptor genes showing differential expression and diagnostic utility 6. In endometrial carcinoma, elevated HTR3C expression associates with microsatellite-stable tumors and higher-risk disease phenotypes 7. These findings suggest HTR3C dysfunction contributes to disorders involving serotonergic dysregulation and may serve as a therapeutic target for gastrointestinal and neurological conditions.