Sensory determinants of suckling behavior in weanling rats

Exteroceptive determinants of nipple attachment in albino rat pups were studied by altering maternal sensory features. Rats 15, 20, 25, and 30 days of age were permitted to locate and attach to the nipples of their anesthetized mother after she had received one of the following treatments: (a) thermalnipple and peripheral skin temperatures were lowered to either 31 or 28 degrees C, (b) tactile--the mother's ventrum was shaved clean; (c) thermotactile--the mother was shaved, and her peripheral temperature was lowered to 31 degrees C; and (d) olfactory--all nipples were thoroughly cleaned with methylene chloride and ethanol solvents. Only the nipple-wash treatment consistently affected nipple attachment. Washing the nipple disrupted suckling; returning a vacuum distillate of the wash extract or of pup saliva reinstated attachment to normal levels. Thus, in sighted weanling rats, as in younger rat pups, olfactory stimuli remain the major determinants of nipple attachment.