Neonatal chorda tympani transection alters adult preference for ammonium chloride in the rat.

The immature gustatory system of the neonatal rat is characterized by sensitivity to disruption by early interventions such as receptor or nerve damage. The present studies examined the effect of chorda tympani transection (neoCTX) of neonates on adult preference for salt and nonsalt stimuli. NeoCTX at 10 days of age led to a striking change in adult rats' preference for NH4Cl solutions but little change in preference for other solutions, including NaCl and KCl. Permanent anatomical effects of neoCTX included failure of the nerve to regenerate and a loss of all fungiform taste buds. Preference for NH4Cl was not due to an inability to discriminate it from NaCl. Following taste aversion conditioning to NaCl, neoCTX rats clearly distinguished between NaCl and NH4Cl. The effects on NH4Cl preference reflect a sensitive period during development because adult rats receiving similar surgery did not show any change in NH4Cl preference.