V1 Receptor 

V1 receptor signaling is mainly represented by V1aR and V1bR, two arginine vasopressin receptor subtypes that mediate physiological functions beyond renal V2R antidiuresis, including cardiovascular homeostasis, hormone secretion, and social behavior^[1]. Mechanistically, V1aR is originally found in vascular smooth muscle, whereas V1bR is originally found in the anterior pituitary, providing an isoform-level distinction for experimental design^[1]. In disease and behavioral models, male V1aR knockout mice show markedly reduced anxiety-like behavior and profound impairment in social recognition, while V1aR re-expression in the lateral septum rescues social recognition^[2][3]. Compared with OTR, V1bR, and V2R, selective V1aR ligands remain important because receptor and peptide homology can limit subtype-specific interpretation^[4]. For experimental applications,^[D-Arg8]-inotocin acts as a stable competitive V1aR antagonist with 3,000-fold binding selectivity over OTR, V1bR, and V2R^[4].