Effects of early postnatal sibling deprivation on anxiety and vulnerability to cocaine in offspring rats.

RATIONALE

Early-life experience has long-term consequences on affective behavior and drug abuse in adults. While many manipulations used to study these consequences alter mother-infant interactions, the effects of sibling interactions are less well characterized.

OBJECTIVES

To examine the long-term effects of early postnatal sibling deprivation (EPSD) on anxiety-like behavior, sucrose preference and behavioral responses to cocaine in adult rats.

MATERIALS AND METHODS

After EPSD manipulation, in which litters were culled to one pup on postnatal day 1 (PN1) or 7 (PN7), the dams' maternal behavior was observed. After the pups reached adulthood, we tested their behavioral responses in the elevated plus maze and sucrose consumption, and to cocaine conditioned place preference and cocaine sensitization.

RESULTS

The pups with EPSD on PN1 received more maternal licking/grooming during the first postnatal week. EPSD on PN1 but not PN7 enhanced locomotor activity in the open field test and exploration of open arms in the elevated plus maze in both female and male offspring. While EPSD had no effect on sucrose intake in adult rats, it decreased vulnerability to cocaine sensitization and cocaine conditioned place preference in male but not female rats.

CONCLUSION

Our findings that early postnatal sibling deprivation influences maternal licking/grooming behavior, as well as anxiety-like behavior and vulnerability to drugs in pups that have grown to adulthood, suggests that both sibling interaction and maternal behavior, play critical roles in individual development.