Manipulation of the dopamine system affects fetal and neonatal responses to an artificial nipple.

Rat fetuses respond to stimuli that they will encounter later while suckling. When exposed to an artificial nipple (AN) E21 fetuses show overall behavioral activation, mouthing, facial wiping, and oral grasping of the AN. The present experiments examined fetal and neonatal responses to the AN after central nervous system injection of receptor-binding drugs for the dopamine system. The D2 agonist drug quinpirole increased appetitive responses to the AN in the fetus and neonate. Activity at the D2 dopamine receptor promotes expression of fetal behavioral responses that are similar to those shown by the neonatal rat at the nipple. Motor responses also were elicited in neonatal pups that normally do not attach to the artificial nipple. These findings suggest that the dopamine system may regulate oral capture of the nipple in the neonatal rat.