Glutamate plays a double role in the physiology of TRCs. As a free-occurring component of some foodstuff, glutamate is detected by TRCs and conveys information about the presence of protein-rich source. As a substance released by TRC and/or nerve endings, it is involved in cell-to-cell communication at chemical synapses in taste organs. In both cases, glutamate is sensed by TRC membrane through specific receptors, some of which (iGluRs) are similar to those found in the CNS, whereas others (taste-mGluR4 and T1R1/T1R3) are specifically expressed by TRCs. One interesting aspect of the biology of glutamate receptors in TRCs is that their expression seems to depend on the specific papillary localization of TRCs. For example, T1R1/T1R3 receptors are found predominantly in fungiform papillae but not in the foliate/vallate papillae of the mouse. Evidence for taste-mGluR4 has been obtained, on the other hand, by analyzing foliate/vallate papillae in rat. It is then reasonable to conceive that food glutamate may give rise to different patterns of TRC activation depending on their localization on the tongue surface. This may have a profound impact on the sensory coding for glutamate compared to other taste stimuli, including the central representation of this substance as “umami” taste.