Maternal behavior in rats and the effects of neonatal progestins given to the pups.

This paper reports changes in maternal behavior of rats following progestin treatment of the neonates. There have been recent reports that hormonal treatment of pups can alter maternal behavior, particularly licking of pups, and that such effects might have implications for the later development of those pups. Accordingly, the major objective of the experiments described was to test the hypothesis that the effects of neonatal progestins on later behavioral development that we have previously described (Birke & Sadler, 1983; 1984) might in part be mediated by changes in maternal behavior. This was done by investigating the behavior of dams, including pup-directed behavior, following the hormone treatments that we have used previously. In the first experiment, medroxyprogesterone acetate (MPA), given via maternal milk, was found to increase rates of pup licking by dams. In the second experiment, anogenital licking was increased to litters containing pups that had received either MPA or progesterone by direct injection. No significant changes in licking following pup treatment with the antiserum to progesterone were observed, however. The results are discussed in relation to our previous work on progestin effects on later behavior, and in relation to the suggestion that hormonal effects on sexually dimorphic behaviors might, at least partly, be mediated through interactions with the mother during the neonatal period.