Effect of Quinine Solutions on Intracellular Ca2+ Levels in Neuro-2a Cells—Conventional Physiological Method for the Evaluation of Bitterness

The purpose of the present study was to examine the effect of quinine on intracellular Ca2+ ([Ca2+]i) levels in cultured neuro-2a cells, and to investigate the possibility of using [Ca2+]i levels to predict the bitterness of quinine solutions. [Ca2+]i levels in neuro-2a cells increased following stimulation by quinine in a concentration-related manner. There was a good linear correlationship between the quinine-induced increase in [Ca2+]i levels increase and the bitterness scores of the quinine solutions as assessed in human gustatory sensation tests (r2=0.918). The quinine-induced increase in [Ca2+]i levels was inhibited by thapsigargin (an inhibitor of the Ca2+ pump into intracellular stores), U73122 (an inhibitor of phospholipase C) and ω-conotoxin (an N-type Ca2+-channel blocker), but not by nifedipine (an L-type Ca2+-channel blocker).