Developmental changes in suckling of rat pups

Abstract

ONTOGENETIC analysis of mammalian suckling provides a unique opportunity to observe the emergence of appetitive behaviour. Transitions in the nature of suckling may reveal progressive stages in the development of adult ingestive systems. Unfortunately, little information is available regarding the nature of suckling behaviour as it develops, and is eventually replaced by feeding and drinking, because it has proved difficult to separate the behaviour of the altricial infant from the contribution of the mother to the nursing dyad. We report here the developmental characteristics of, and changes in, the behaviour of suckling rats as they locate, apprehend and suckle the nipples of anaesthetised dams. This situation permits the detailed evaluation of rat pup behaviour in isolation from the active maternal role. Even at birth, pups are capable of quickly apprehending and suckling the nipples of an anaesthetised dam. Suckling then undergoes two major transitions. The first, after day 10 post partum, suggests the emergence of a physiological control of suckling behaviour. The second, beginning after day 14, indicates a changing responsiveness to some characteristic of the mother's nipples or milk ejection.