Figure 6. Acid taste stimulation evokes 5-HT release from presynaptic (Type III) taste cells.

A, recording of Ca²⁺ responses in a presynaptic cell (PRE) and from a closely apposed 5-HT biosensor cell (5-HT Bio). Bath-applied acetic acid (HOAc, bar at bottom of traces, 10 mm, pH 5.0) evoked Ca²⁺ responses in the presynaptic cell (top trace) and, after a brief delay, in the biosensor cell (bottom trace), indicating 5-HT secretion. Responses in the presynaptic and 5-HT biosensor cells alike were abolished when Ca²⁺ was replaced with Mg²⁺ in the bathing solution (0 Ca, dashed lines). B, summary of data. Bars represent means ±s.e.m. of individual responses. All responses were normalized to the (pooled) mean KCl response for all experiments in the series (n = 11). Filled bars, data from presynaptic cells. Open bars, corresponding data from the apposed 5-HT biosensor cells. *P < 0.05