Low environmental temperature modulates gustatory nerve activity and behavioral responses to NaCl in rats

We studied the effects of cold ambient temperature on chorda tympani nerve responses to taste stimuli such as sucrose, NaCl, quinine HCl (QHCl), and HCl in rats. The electrophysiological recordings of the whole chorda tympani nerves from control (22 degrees C) and cold-exposed (4 degrees C) rats revealed that the responses to sucrose, HCl, and QHCl were unaffected by cold exposure. In contrast, the nerve responses to NaCl were enhanced time dependently, reaching a maximum 7-14 days after cold exposure. Responses to sodium acetate were likewise elevated as they were to NaCl, whereas those to KCl were unchanged after cold exposure. In addition, the residual NaCl responses after lingual application of the sodium-channel blocker amiloride in cold-exposed rats were similar to those in control animals. It is thus most likely that cold exposure potentiates the chorda tympani nerve responses to Na(+), but not to Cl(-). Behavioral studies with the two-bottle preference test showed that the cold-exposed rats refused to drink NaCl solutions at 0.05 and 0.1 M, the concentrations being preferred by control animals. These results suggest that the ambient temperature influences taste cell function, and that the enhanced NaCl response of the chorda tympani nerve is related to the avoidance of NaCl intake under cold environment.