(A) Targeting strategy for generating V1aR^iCre knock-in mouse line. (B) Genotyping confirmation of wild-type and iCre positive mice. (C and D) Expression patterns (C) and coexpressing analysis (D) of V1aR mRNA and iCre mRNA in the CeM of V1aR^iCre mice. (E) Schematic of viral injection, fiber implantation, and jGCaMP7s expression in the CeM. (F) Schematic of fiber photometry recording during social interaction. (G) Continuous Ca²⁺ signals of V1aR^jGCaMP7s neurons during the initial social investigation (yellow shadowed), allogrooming (blue shadowed) and allolicking (pink shadowed). (H–J) Heatmaps (H), average traces (I), and mean ΔF/F (J) showing Ca²⁺ dynamics of V1aR^jGCaMP7s neurons in response to naive and melittin-treated cagemates. (K–M and N–P) Heatmaps (K and N), average traces (L and O), and mean ΔF/F (M and P) showing Ca²⁺ dynamics of V1aR^jGCaMP7s neurons before (baseline) and during allogrooming (K–M) or allolicking (N–P) episodes. (Q) Comparison of mean ΔF/F Ca²⁺ signals in V1aR^jGCaMP7s neurons during allogrooming and allolicking episodes. (R–T) Heatmap (R), average trace (S), and mean ΔF/F (T) showing Ca²⁺ dynamics of V1aR^jGCaMP7s neurons before (baseline) and during self-grooming episodes. Scale bars: 100 μm (original in C and E), 50 μm (magnified in C). Data are mean ± SEM. All mice are male. n = 3 mice in D; n = 12 or 17 trials from 7 mice in H–J; n = 25 trials from 5 mice in K–M; n = 11 trials from 5 mice in N–P; n = 16 trials from 5 mice in R–T. Statistical results are included in Supplemental Table 2. Mann Whitney U test for J and Q; Wilcoxon matched-pairs test for M and T; Paired t test for P.