Genetically variable taste sensitivity to D-amino acids in mice

Behavioral and neural responses to D-amino acids were compared between two inbred strains, C57BL and BALB mice. In both strains, an aversion conditioned to D-valine, D-leucine, D-methionine, D-histidine or D-tryptophan generalized to sucrose, whereas an aversion to D-alanine or D-serine did not generalize to sucrose. Generalization patterns across various test stimuli for each of these 7 D-amino acids were significantly correlated between two strains. However, an aversion conditioned to D-phenylalanine generalized to sucrose in C57BL mice, but not in BALB mice. Application of a proteolytic enzyme, Pronase E, to the tongue reduced chorda tympani responses to sucrose and D-amino acids to which a conditioned aversion generalized to sucrose. Again, only in C57BL mice, Pronase inhibited D-phenylalanine responses. These comparable results indicate that sweet taste response is genetically highly variable only to D-phenylalanine among 8 D-amino acids tested.