An intrinsic source of behavioral regulation that influences discrete responses to cues important for the initiation of suckling

The present experiment investigated the relationship between motor activity and oral grasping of an artificial nipple in newborn rats. Pups orally grasped the artificial nipple, and they performed more and longer oral grasps in the latter portion of the nipple presentation. Motor activity was cyclical, and this cyclicity was evident before and during presentation of the artificial nipple. The onset of an oral grasp response was preceded by a period of relatively low motor activity, and the termination of a grasp was followed by relatively high motor activity. The newborn rat pup's intrinsic oscillations in motor activity may regulate the expression of discrete responses to cues important for the initiation of suckling. Late-gestation fetal rats respond to suckling stimuli including milk and an artificial nipple (AN) with species-typical behavioral patterns such as the stretch response to milk (Robinson & Smo-therman, 1992, 1994) and oral grasping of an AN (Robinson, Hoeltzel, Cooke, Umphress, Murrish, & Smotherman, 1992). Not only do these fetal responses highlight that the origins of appetitive behaviors of the neonate begin in utero, but they also raise new questions about postnatal behavior. In the present study, we in