Figure 3.

ATP is released from taste cells via channels. (A) ATP secretion triggered by depolarization (upper insets) was apparently independent of Ca²⁺. Upper traces: ATP release from the same cell was weakly dependent on extracellular Ca²⁺. Bottom traces: ATP secretion from the same cell was not diminished by dialysis with 10 mM BAPTA (left panel) or by the drop in extracellular Ca²⁺ (right panel). The patch pipette contained 140 mM CsCl, 2 mM K₂ATP, and 10 mM BAPTA. (B) Responses of the ATP sensor to serial depolarization of a taste cell to specific potentials (indicated above the traces) for 5 s. (C) ATP responses (Δ) of COS-1 cells as a function of taste cell depolarization from −70 mV to indicated voltage for 5 s. The responses of the ATP sensor correlate well with the integral conductance G of taste cells (•) calculated by the equation I=G(V−V_r), where I, V, and V_r are sustained current, membrane voltage, and reversal potential, respectively. The data are presented as mean±s.d. (n=3–7). In (A (upper trace), B, C), the recording conditions were as in Figure 1E.