THERMAL, OLFACTORY, AND TACTILE STIMULI INCREASE ORAL GRASPING OF AN ARTIFICIAL NIPPLE BY THE NEWBORN RAT

Caesarean-delivered rat pups tested before any suckling experience sho w oral grasp responses after stimulation with an artificial nipple. Ma nipulating the sensory stimuli present at the time of testing alters b ehavioral responses to the nipple. Specifically, when the nipple is wa rm, when pups are tested in the presence of amniotic fluid or milk odo r, or when pups are tested in the presence of a conspecific, oral gras ping of the artificial nipple is increased. Pups respond to the nipple with a shorter latency, show more oral grasp responses, and the indiv idual grasp responses are longer in duration. The experiments suggest that the newborn rat pup exhibits a basic set of behaviors in response to the nipple early in development and that sensory stimuli normally present during the expression of suckling increase oral appetitive beh aviors evoked by the nipple. (C) 1998 John Wiley & Sons, Inc.