Fig. 3

Requirements for 4MT-preference acquisition. (A) Preference index for 4MT was analyzed in oil-nip-conditioned (n = 8) and 4MT-nip-conditioned pups (n = 7) in oxytocin receptor (OTR) heterozygous knockout (left), and in oil-nip- (n = 6) and 4MT-nip-conditioned pups (n = 9) in OTR homozygous knockout (right). OTR homozygous knockout mice showed normal 4MT-preference acquisition. (B) Frequencies of dams’ lactation for three or more pups (left) and immobility without lactation (right) during 1–30 min (upper) and 31–60 min (lower) after oil (n = 21), 4MT (n = 21), or EG-nip painting (n = 18) during P13-15 were counted. During 1–30 min dams painted with 4MT displayed a significant decrease in the frequency of lactation and a significant increase in immobility. (C) Preference index for 4MT in oil-dam-unpaired (Oil-DUP, n = 19), 4MT-dam-unpaired (4MT-DUP, n = 32), 4MT-dam-paired (4MT-DP, n = 17), and 4MT-dam/sibling-unpaired conditionings (4MT-DSUP, n = 16). Pups in 4MT-DUP and 4MT-DP conditionings showed a significant preference for 4MT while those in 4MT-DSUP conditioning showed no preference. (D) Preference index for 4MT at P11–18 in oil-DUP- and 4MT-DUP-conditioned pups conditioned during P12-18. Pups in 4MT-DUP conditioning displayed significant aversion at P13 and significant preference at P17 and P19, while those in oil-DUP conditioning displayed significant aversion at P17 and P19. Welch’s unpaired t-test (A, D), Dunn’s multiple comparison test (B), Tukey’s multiple comparison test (C): *, p < 0.05; **, p < 0.01; ***, p < 0.001; ****, p < 0.0001. OST (A, C, D): $, p < 0.05; $$, p < 0.01; $$$, p < 0.001.