Maternal behavior of female rats with 6-OHDA lesions in the ventral striatum: characterization of the pup retrieval deficit.

The present experiments characterized the impairment in pup retrieval previously observed in maternal rats following dopamine-depleting 6-hydroxydopamine (6-OHDA) infusions in the ventral striatum. Video recordings of 30-min pup retrieval tests revealed that 6-OHDA mothers spent most of the time feeding (Experiment 1). Denying the mothers the opportunity to eat during testing failed to reestablish pup retrieval. Similarly unsuccessful was an attempt to evoke food-motivated pup retrieving in 6-OHDA mothers by coating the stimulus pups' skin with a 4% sucrose solution (Experiment 2). However, restoration of pup retrieval was observed in 6-OHDA mothers that had been separated from their pups for 3-6 h (Experiments 3 and 4). Stimulation of ultrasonic callings by clonidine treatment of the stimulus pups, or leaving pups in the nest during testing, were not significantly effective (Experiment 3). These data suggest that separation-induced increases in maternal motivation can override the inhibitory effect of ventral striatal dopamine depletion on pup retrieval.