Ion transport in rat tongue epithelium in vitro: a developmental study.

The responsiveness of the rat gustatory system to monochloride salts changes during development. Neurophysiological recordings in the chorda tympani indicate that a) the taste responses to NaCl and KCl in early postnatal rats are small relative to NH4Cl, b) both salts become more potent stimuli as the animal matures, and c) the developmental increase is accompanied by an increase in sensitivity of the NaCl response to the sodium transport blocker amiloride. We measured ion transport properties of in vitro tongue epithelia from Wistar rats. When the tissue is mounted in an Ussing chamber, the short-circuit current responses to NaCl and KCl are small in the neonatal rat and increase during development in postweaning and adult animals. Amiloride sensitivity of the NaCl response also increases with age. This study confirms that increased sensitivity of the rat gustatory system to NaCl with age reflects changes in the peripheral membranes. The results support hypothesis that the increased sensitivity is due to amiloride-sensitive membrane components being added or becoming functional.