Retention of maternal behavior in nulliparous and primiparous rats: Effects of duration of previous maternal experience.

Abstract

The effects of duration of prior maternal experience on the retention of short-latency maternal behavior in rats was studied. Lactating primiparous and nonlactating pup-induced-maternal nulliparous female rats were given 1, 4 or 9 days of maternal experience with rat pups before the females were isolated from the young. Twenty-five days later females were reexposed to 3-8 day old foster pups and latencies to show maternal behavior in the home cage and a T maze test were scored. In the home cage the latencies of all nulliparous groups were shorter upon reinduction. Increasing the length of prior maternal experience did not result in further reduction in maternal latencies in either nulliparous or primiparous females. Comparisons of primiparous and nulliparous groups revealed that primiparous females (1, 4 and 9 days combined) carried a pup, crouched, retrieved and grouped the pups, and built a good nest faster than did nulliparous females (combined groups). The number of behavioral differences between specific primiparous and nulliparous groups decreased as the length of prior maternal experience increased. In the T maze the percentages of reinduced nulliparous and primiparous females that retrieved pups did not differ, although latencies to retrieve a pup were shorter in primiparous females. The similarities in the behavioral responses of primiparous and nulliparous females indicate that the processes underlying establishment of the long-term retention of short-latency maternal behavior in these groups may be comparable.