RT Journal Article SR Electronic T1 Bitter Taste Transduction of Denatonium in the MudpuppyNecturus maculosus JF The Journal of Neuroscience JO J. Neurosci. FD Society for Neuroscience SP 3580 OP 3587 DO 10.1523/JNEUROSCI.17-10-03580.1997 VO 17 IS 10 A1 Ogura, Tatsuya A1 Mackay-Sim, Alan A1 Kinnamon, Sue C. YR 1997 UL http://www.jneurosci.org/content/17/10/3580.abstract AB Bitter substances are a structurally diverse group of compounds that appear to act via several transduction mechanisms. The bitter-tasting denatonium ion has been proposed to act via two different G-protein-regulated pathways, one involving inositol 1,4,5-trisphosphate and raised intracellular calcium levels, the other involving phosphodiesterase and membrane depolarization via a cyclic nucleotide-suppressible cation channel. The aim of the present study was to examine these transduction mechanisms in taste cells of the mudpuppy Necturus maculosus by calcium-imaging and whole-cell recording. Denatonium benzoate increased intracellular calcium levels and induced an outward current independently of extracellular calcium. The denatonium-induced increase in intracellular calcium was inhibited by U73122, an inhibitor of phospholipase C, and by thapsigargin, an inhibitor of calcium transport into intracellular stores. The denatonium-induced outward current was blocked by GDP-β-S, a blocker of G-protein activation. Neither resting nor denatonium-induced intracellular calcium levels were affected by inhibition of phosphodiesterase (with IBMX) or adenylate cyclase (with SQ22536) or by raising intracellular cyclic nucleotides directly (with cell permeant analogs). Our results support the hypothesis that denatonium is transduced via a G-protein cascade involving phospholipase C, inositol 1,4,5-trisphosphate, and raised intracellular calcium levels. Our results do not support the hypothesis that denatonium is transduced via phosphodiesterase and cAMP.