A bitter substance denatonium increases calcium levels in a taste cell

Pseudo color images of Ca2+ levels in a taste receptor cell.

Taste signal transduction mechanisms and modulation
Taste sensation is critical for intake of nutritious foods and avoidance of toxic substances.

We have been studying how taste receptor cells transduce chemical information of taste substances into intracellular signals including Ca²⁺ levels (Fig. 1) and ionic currents.

 Sensitivity of taste is influenced by body mass, nutritional condition, hormonal levels, medication etc.  Our current working hypothesis is that a neurotransmitter acetylcholine modulates taste responses in taste buds.  We are using Ca²⁺ imaging, immunohistochemistry and electrophysiological techniques with normal and genetically modified mice for this study.  We have found that taste receptor cells increase Ca²⁺ levels in response to acetylcholine (ACh, Fig. 2) via activating muscarinic acetylcholine receptors.  Since our data indicate that both responses to bitter substances and acetylcholine share the similar signal transduction pathway in the taste cells, acetylcholine could interact with bitter taste response resulting in modulation of taste.  Currently, we are working on the source of acetylcholine and identifying the subtype of acetylcholine receptors involved.