Isolated taste bud were sequentially depolarized with KCl, stimulated with tastants and with ATP, in the absence or presence of 10 μM GABA. A, Traces show stimulus-evoked 5-HT release from Presynaptic cells within the taste bud (i.e., responses from a 5-HT biosensor apposed to the taste bud). All stimuli (arrows) elicit 5-HT release as shown previously (Huang et al., 2007). GABA has no effect on ATP-evoked 5-HT release. B, same taste bud, showing effects of GABA on taste-evoked 5-HT release. Here, Presynaptic cells are indirectly triggered to release 5-HT and GABA-mediated inhibition is consistent with GABA acting to reduce ATP release from Receptor cells, thereby interfering with cell-cell excitation of Presynaptic cells. C, summary of several experiments as those in A,B. Details of bars and analyses as in Figure 1.