Effects of acute hypergravity exposure and parity on maternal behavior in CD-1 mice

We assessed the behavioral response to acute hypergravity exposure in lactating mother mice, Mus musculus of the outbred CD-1 strain. Primiparous or terziparous dams were exposed with their litters to a centrifugal force equivalent to 2G hypergravity for 1 h daily from postnatal day 2 (P2) to P9. We made detailed behavioral observations before, during and after the rotation on selected days to identify elements of the maternal behavioral repertoire vulnerable to 2G challenge. Licking and nest building were reduced during rotation while mothers sniffed and snouted their pups more. Nursing and total time in physical contact with pups were relatively stable. The effects of rotation were most pronounced on P2, dams appearing to habituate to the treatment with repeated exposure. Dam parity had a limited effect on the behavioral response to rotation, primiparous mothers tending to spend longer nursing their pups during the rotation and showing a greater tendency to lick and nest-build in post-rotation. Differences between parity groups diminished over days. Body weight was decreased in rotated primiparous dams and their pups gained less weight than stationary controls. Ultrasonic vocalization (USV) rates recorded on P2, P5 and P9 seemed to indicate delayed behavioral development in rotated pups.