Modification of behavioral and neural taste responses to NaCl in C57BL/6 mice: effects of NaCl exposure and DOCA treatment

Abstract

To investigate the possible role of peripheral gustatory responsiveness to changes in NaCl acceptance, we studied NaCl consumption and the chorda tympani nerve responses to lingual application of NaCl in C57BL/6ByJ mice. The mice were treated with 300 mM NaCl (given to drink in 96-h two-bottle tests with water) or with injections of deoxycorticosterone acetate (DOCA; 33 mg/kg daily). Naive mice were neutral to 75 mM NaCl, but mice previously exposed to 300 mM NaCl avoided 75 mM NaCl. The NaCl-exposed (300 mM for 4 days and 75 mM for 2 days) mice had enhanced amiloride-sensitive components of the chorda tympani responses to 10-30 mM NaCl applied at room temperature (24 degrees C). DOCA injections increased acceptance of 300 mM NaCl, but did not change the chorda tympani responses to 100-1000 mM NaCl. However, the DOCA-treated mice had enhanced amiloride-sensitive components of the chorda tympani responses to cold (12 degrees C) 10-30 mM NaCl. These data suggest that peripheral gustatory responsiveness possibly contributes to the NaCl aversion induced by exposure to concentrated NaCl, but not to the DOCA-induced increase of NaCl acceptance.

FIG. 1

Effect of DOCA on fluid intake (upper three rows) and 300 mM NaCl preference (bottom row; means ± SE). Letters show significant difference (p < 0.05, planned comparisons) relative to the first five baseline days (b) or last 4 posttreatment days (p) of the experiment.

FIG. 2

The chorda tympani responses of control, NaCl-exposed and DOCA-treated mice to NaCl at different temperatures (relative to 100 mM NH₄Cl; means ± SE). Top: magnitudes of responses to NaCl and its mixtures with 0.1 mM amiloride. Bottom: amiloride-sensitive components of the responses. Asterisks with lines show significant differences between groups (p < 0.05, planned comparisons).

FIG. 3

The chorda tympani responses (relative to 100 mM NH₄Cl; means ± SE) of control, NaCl-exposed and DOCA-treated mice to KCl and its mixtures with 0.1 mM amiloride at different temperatures.