FIG. 1.

p-Trifluoromethoxy-phenylhydrazone (FCCP) application causes a variable change in cytosolic calcium levels in taste cells. A: application of the protonophore, FCCP (black bar), reversibly eliminated the mitochondria's ability to buffer calcium. Application of FCCP caused increases in cytosolic calcium levels in 94% of previously unstimulated taste cells (n = 536). The amplitude of the response varied among different cells as shown here. Two taste cells simultaneously stimulated by FCCP evoked very different amplitudes in their calcium responses. B: amplitudes of the FCCP-induced calcium responses varied significantly across different populations of taste cells. Taste cells that release calcium from internal stores in response to bitter stimuli but lack voltage-gated calcium channels (VGCCs) had significantly smaller FCCP-dependent calcium responses compared with taste cells with VGCCs (P = 0.0009) or taste cells that were not responsive to taste stimuli and did not express VGCCs (labeled “neither,” P = 0.02). Taste cells that responded to bitter stimuli (via calcium release from internal stores) and have VGCCs generated significantly smaller calcium elevations in response to FCCP compared with taste cells that only have VGCCs (P = 0.046). No other significant differences in the FCCP-dependent calcium responses were found. C: prolonged FCCP application (9 min) caused a sustained increase in cytosolic calcium that was maintained until FCCP was washed out and the mitochondria were able to buffer [Ca²⁺]_i. D: an example FCCP-induced calcium elevation in a taste cell that expresses VGCCs as measured by its sensitivity to high KCl (50 mM). E: an example FCCP-induced calcium elevation in a taste cell that releases calcium from internal stores in response to bitter stimuli. F: an example FCCP-induced calcium elevation in a taste cell that releases calcium from internal stores in response to bitter stimuli and expresses VGCCs.