Oral grasping of a surrogate nipple by the newborn rat.

Newborn rat pups exhibit oral appetitive behaviors when presented with an artificial nipple. These behaviors include mouthing and licking movements and expression of stereotyped oral grasp response. Caesarean-delivered pups show increased responding to the nipple over the first 5 h after birth that is independent of experience with the nipple. Mimicking maternal licking by stimulating the anogenital region of the newborn rat with a soft paintbrush increases response to the nipple. Pups tested after 24 hr of normal experience respond to the artificial nipple when tested immediately after separation from the mother. However, oral grasping of the nipple is more frequent in 1-day-old pups tested 3 or 5 hr after separation from the mother. Study of behavioral responses to the artificial nipple promises to provide information about sensory and neurochemical controls of the initial suckling episode.