NMDA receptor in intestinal enteroendocrine cell, STC-1

We earlier showed that intestinal STC-1 cells can respond to five basic taste stimuli. Here, we investigated which receptors or channels are involved in the sensing of umami in STC-1 cells. T1R family and metabotropic glutamate receptors were not involved. In contrast, we found that N-Methyl-D-aspartate (NMDA) receptors are expressed in STC-1 cells by RT-PCR analysis. Using a calcium-imaging technique, we also observed that a specific agonist NMDA induces the increase in the intracellular Ca concentration in STC-1 cells. We also found that pretreatment with NMDA enhances sweet-induced response in STC-1 cells, suggesting important roles of L-Glu-signaling in the chemosensory system of the gastrointestinal tracts.