The nucleus accumbens shell is critical for normal expression of pup-retrieval in postpartum female rats

The nucleus accumbens (NA) plays an important modulatory role in the control of normal expression of maternal behavior (termed maternal performance). The present study investigated the relative functions of two subregions of the NA (the shell and core) in maternal performance. Electrolytic lesions of the shell or core were performed either before parturition or immediately after a varying amount of maternal experience (none, 1 or 24h) during the immediate postpartum period. Maternal performance was tested on Day 1 postpartum and re-tested 9 days later using a pup sensitization technique. Results show that lesions of the shell, but not the core, significantly disrupted pup-retrieval: the shell-lesioned rats took significantly longer to finish retrieving all test pups, but their retrieval latency for the first pup was not affected. Neither lesion affected other components of maternal behavior (pup licking, nest building and nursing). These findings suggest that the shell, but not the core, is critical for the normal expression of pup-retrieval behavior possibly through its role in maintaining maternal motivation or attention.