Changes in serum prolactin and corticosterone in induced maternal behavior in rats

Abstract

Maternal behavior (nest-building, retrieving and nursing) was induced and maintained in virgin rats by continuous exposure to young (3–7 days old) pups for 10 and 30 days. Maternally behaving rats on diestrus 1 were then deprived of young for 5 hr and bled by decapitation at 14:30. A similar group of maternally behaving rats was pup-deprived for 5 hr, but again exposed to young rats from 14:30 to 15:30 before decapitation. Similar protocols were followed in naive virgin rats, in parturient mothers on the 10th day of lactation, and in multiparous mothers approximately 5 months after their last delivery or exposure to pups. No significant difference in serum prolactin levels was found at 14:30 in maternally behaving rats when compared with virgin or multiparous animals. By 15:30 the one hr re-exposure to young rats had increased prolactin levels in maternally behaving animals, a tendency similar to that observed during actual maternal behavior in lactating mothers. Initial presentation of pups to either naive virgin or non-lactating multiparous rats resulted in reduced prolactin levels and increased corticosterone concentrations one hour later. In addition, corticosterone levels were elevated at 14:30 in maternally behaving and parturient rats deprived of young for 5 hr. These data show that an inverse relationship exists between serum corticosterone and prolactin levels in non-maternal females one hour after novel exposure to pups, and that these hormonal relationships can be altered considerably following induction of maternal behavior over a 10 or 30 day period. It is significant that the gross behavior which is induced by specific sensory information is associated with a hormonal release pattern similar to that occurring in actual maternal behavior.