Suckling in newborn rats: eliminated by nipple lavage, reinstated by pup saliva.

Chemical lavage of the nipples of anesthetized maternal rats virtually eliminated suckling by their 4- to 5-day-old pups. Normal suckling was immediately reinstated, however, by painting a vacuum distillate of the wash or of pup saliva onto the nipples. Thus, a substance necessary to direct and release suckling, possibly rat pup saliva, appears to coat the nipple surface.