Chorda tympani responses to gustatory stimuli in developing rats

Abstract

The developmental change in rat taste sensitivity during theperiod from the 2nd to the 12th postnatal week was studied by recordingthe responses of the chorda tympani nerve to lingual stimulation by NaCl, LiCl, KCl, NH4Cl, HCl, quinine hydrochloride (Q-HCl), and sucrose. The threshold for all stimulants except sucrose was lower in the 3-week-old rats than in the 12-week-old ones.The order of the magnitudes of the normalized neural responses to the 0.1 M monochloride salts of thegustatory nerves was NH4Cl>NaCl=LiCl>KCl in the 3-week-old rats, and NaCl=LiCl>NH4Cl>KCl in the 12-week-old rats. The magnitude of the normalized responses to NH4Cl, HC1, and Q-HCl at nearly allconcentrations was greater at 3 weeks than at 12 weeks, while the magni-tude of the responses to NaCl and LiCl at high concentrations was lesserat 3 weeks than at 12 weeks. Changes in the gustatory sensitivity tovarious taste stimuli during development can be classified into the following two types:(1) sensitivity-decreasing type the magnitude of theresponse to NH4Cl, Q-HCl, and HCl was greatest during the first fewweeks and decreased thereafter, and (2) sensitivity-increasing typethe magnitude of the response to NaCl, LiCl, and sucrose showed anincrease accompanying the growth of rats from around the 2nd weekafter birth. © 1980, PHYSIOLOGICAL SOCIETY OF JAPAN. All rights reserved.