Figure 1.

Confocal imaging in lingual slices of taste cells responding to sweet, bitter and umami tastants. A, Micrograph of a lingual slice containing a vallate papilla, showing taste cells loaded with calcium green dextran (CaG dextran). Dashed line outlines the vallate crypt along which are embedded the taste buds (two examples outlined with dotted lines). B, Stimulation (arrows) of identified Receptor (type II) taste cell with mixture of sweet compounds SC45647 and saccharin, produces Ca²⁺ responses that are enhanced by the presence of adenosine (50 μm, present throughout the shaded area). Note that adenosine itself does not elicit a response. Ordinate, increase in CaG dextran fluorescence relative to baseline (see Materials and Methods). C, Summary of data from experiments as in B. The plot shows magnitude of responses to sweet stimulation before (filled circles) and during the presence of adenosine (open circles). Responses of each cell were normalized to its responses in the absence of adenosine. Student's t test, two tailed, repeated measures, p < 0.02. n = 8 cells. Blue symbols show the mean and 95% confidence interval. D, Ca²⁺ responses in vallate taste cells stimulated with a bitter taste mix (arrows) in absence or presence (shaded area) of adenosine as in B. E, Summary of results as in D, showing that adenosine does not affect bitter-evoked responses, p = 0.40, n = 7 cells. F, As in B, showing Ca²⁺ responses to umami stimulation. G, Summary of data showing that umami-evoked responses are unaffected by adenosine, p = 1.00, n = 9 cells. Calibrations in D and F as in B.