Interacting effects of oxazepam in late pregnancy and fostering procedure on mouse maternal behavior.

The present study was designed to assess the proactive effects of late pregnancy benzodiazepine (BDZ) treatment on maternal behavior in the postpartum period, using cross-fostering procedures to control for the role of changes produced prenatally in the offspring. Outbred CD-1 mouse dams were treated with either oxazepam (OX, 15 mg/kg PO twice/day on pregnancy days 12-16) or vehicle (VEH). After parturition, entire litters were exchanged either within treatments (in-fostered groups, IF) or between treatments (cross-fostered groups, CF), while additional litters were left undisturbed (un-fostered groups, UF). The behavior of lactating dams was observed in their home cages at 4, 8, and 12 days postpartum. Maternal responses, particularly nursing, were reduced in the OX-UF and OX-CF conditions and either normal or enhanced in the OX-IF condition. Correspondingly, locomotor/exploratory activity was markedly enhanced in the former conditions and close to the control level in the latter condition. In sum, the fostering variable appeared to determine whether pups raised by dams treated previously with BDZ receive either insufficient or exaggerated maternal care. This points to the need for a better understanding of mother/pup interactions in studies aimed at characterizing drug and toxicant effects on offspring development.