Learned preferences for the flavor of salted food.

We examined whether rats can associate the flavor of their food with its salt content, and whether this association is influenced by sodium status during training and testing. During two pairs of 2-h training trials, rats ate flavored food containing 1.75% NaCl or an alternatively flavored unsalted food. The motivational state of the rats was manipulated prior to each trial by combined 48-h dietary sodium deprivation and furosemide treatment (severe sodium depletion), 48-h dietary sodium deprivation (mild sodium deprivation), or continued maintenance on stock diet containing 1% NaCl (sodium replete). When later given a choice between the two flavors, all rats preferred food containing the salt-paired flavor. The strength of this preference was unaffected by motivational state during training or by the salt content of the test foods, but was modulated by the motivational state of the rats during the preference test. Preference for the salt-paired flavor was strongest when rats were tested after severe sodium depletion, less strong after mild sodium deprivation, and absent when sodium replete. These results indicate that deprivation state during training has little effect on learned preferences for the flavor of salted food but deprivation state during testing affects the expression of this learning.