Perceptual characteristics of the amiloride-suppressed sodium chloride taste response in the rat

The contribution of amiloride-sensitive membrane components to the perception of NaCl taste was assessed by using a conditioned taste aversion procedure. Eight independent groups of adult rats were conditioned to avoid either 0.1M NaCl, 0.5M NaCl; 0.1M NH4Cl, or 1.0M sucrose while their tongues were exposed either to water or to the sodium transport blocker amiloride hydrochloride. In contrast to rats exposed to water during conditioning, rats exposed to amiloride were unable to acquire a conditioned taste aversion to 0.1M NaCl. Differences in the acquisition of taste aversions between the amiloride- and nonamiloride-treated groups were not apparent when the conditioned stimulus (CS) was 0.5M NaCl, 0.1M NH4Cl, or 1.0M sucrose. Although the magnitude of the 0.5M NaCl aversion was similar between amiloride- and non-amiloride-treated rats, the perceptual characteristics of the CS differed between groups. Analyses of stimulus generalization gradients revealed that amiloride-treated rats generally avoided all monochloride salts after conditioning to 0.5M NaCl but not nonsodium salts or nonsalt stimuli. In contrast, rats not treated with amiloride only generalized the 0.5M NaCl aversion to sodium salts. No differences in generalization gradients occurred between groups when the CS was 0.1M NH4Cl or 1.0M sucrose. These findings suggest that the "salty" taste of NaCl is primarily related to the amiloride-sensitive portion of the functional taste response in rats. Conversely, the portion of the NaCl response insensitive to amiloride appears to have "sour-salty" perceptual characteristics and does not appear to be perceived as being salty.