Activation of basic tastes (sweet, sour, salt, bitter and umami) help identify specific foods and signal dietary content. In spite of their importance to biological functions, little is known about how the taste system detects L-amino acids. It is generally assumed that L-amino acids use the same taste receptor and cellular signal pathway that signals the taste of L-monosodium glutamate, but pilot data suggest that this is too simple. The hypothesis is that multiple taste receptors and two transduction pathways detect and signal L-amino acid tastes. This research will test this hypothesis by comparing taste-related responses to three L-amino acids (L-glutamate, L-serine, L-arginine): 1) of isolated taste sensory cells using calcium imaging methods, 2) of normal mice and mice missing the primary glutamate taste receptor using behavioral methods, and 3) of neurons in the brain stem activated by taste signals from the tongue using antibody markers. Pilot data suggest that at least two (maybe 3) taste receptors detect L-amino acids and the very interesting possibility that cross-talk between two transduction pathways within taste sensory cells modulate L-amino acid tastes. The data also suggest that signals for L-amino acids travel in separate but overlapping neuronal pathways within the brain stem. The results of this research will enable the chemosensory sciences to more directly link the taste qualities of L-amino acids with the biological mechanisms underlying L-amino acid tastes. In turn, this will help health care professionals improve the palatability of foods containing these amino acids, thereby improving dietary intake. Besides the scientific benefits, this project has significant additional broader impacts and will support several undergraduates and two graduate students with opportunities to gain hands-on experience with these research methods and experience the joys of scientific inquiry.
