Chemosensory Transduction Mechanisms in Taste

Taste receptor cells transduce sweet, sour, salty, and bitter chemicals into receptor potentials that ultimately result in the perception of taste. The mechanisms involved in this process are only now beginning to be un­ derstood, with the application of modem physiological and biochemical techniques to these relatively small and somewhat inaccessible receptor cells. The information that is emerging from these studies is that taste cells, like other sensory receptors, utilize apically-located ion channels and receptors for sensory transduction. Unlike most other receptor cells, however, taste cells utilize a diversity of mechanisms for sensory transduction. This diversity reflects, in part, the varied molecular structures of compounds comprising the different taste modalities. Sweet-tasting compounds include carbohydrates and some amino acids, compounds generally important in nutrition. Salt taste is produced by monovalent cations; intake of these compounds is important for maintaining electrolyte balance. A large assortment of molecules produce the bitter sensation. These molecules include divalent cations, alkaloids, some amino acids, and denatonium, the most bitter compound known to man. Bitter-tasting compounds are often toxic, and bitter taste is thought to have evolved as a warning signal that a substance should be avoided. Sour taste is mediated by protons and, finally, umami taste is elicited by monosodium