Figure 3
Effects of postnatal naltrexone (NTRX) treatment on NMRI pups’ indices of attachment behavior during development. (a) Mean number, duration and frequency modulation (difference between the highest and the lowest peak frequency within each element) of ultrasounds emitted by 8-day old pups during 5 min of isolation in a clean or home-cage bedding beaker. NTRX treatment prevents discrimination of nest versus clean bedding only on the basis of mean number of ultrasonic vocalizations (USVs). Sample sizes: NTRX pups in clean bedding: N=10, in home-cage bedding: N=12; SAL pups in clean bedding: N=12, in home-cage bedding: N=10. (b) Percentage of entries (100 × entries mother’s compartment/(entries mother’s compartment + entries unknown mother–litter compartment) and time (100 × time mother’s compartment/(time mother’s compartment + time unknown mother–litter compartment) spent by 10-day old pups in the compartment scented by their mother/nest bedding versus a compartment containing bedding from an unknown mother with its litter. SAL pups significantly preferred their mother/nest compartment, whereas NTRX pups did not. Sample sizes: NTRX male pups: N=12, female pups: N=6; WT male pups: N=14, female pups: N=6. *P<0.05; **P<0.01.
