Figure 4. Cd²⁺-mediated attenuation of voltage-induced changes in C_m in a Type III taste cell.

(A) The sequence of voltage pulses applied to the taste cell clamped at -70 mV. (B) Control depolarization-induced changes in C_m, recorded before the application of Cd²⁺ Tyrode's solution. (C) Depolarization-induced changes in C_m recorded 3 minutes after the application of a Tyrode's solution containing 0.5 mM Cd²⁺. (D) Recovery of depolarization-induced changes in C_m following 5 min wash of the cell with Tyrode's. The traces in B, C and D were low pass filtered (100Hz, Gaussian filter). (E) Average amplitude of depolarization-induced increases in C_m, determined from the last 5 voltage pulses (-20 mV to + 20 mV) on 5 cells was significantly reduced (P<0.05) after the application of Cd²⁺. There was a significant (* P<0.05; one way ANOVA with Tukey's Multiple Comparison Test), recovery after washout of the Cd²⁺ Tyrode's. (F) Time-dependent amplitude reduction of depolarization-induced C_m in Type III taste cells (n = 6 cells). The voltage pulse protocol was applied to a single cell in 5 minute intervals. The response in C_m was averaged for the voltage pulses from -20 to +20 mV. The line represents the best fit to the equation of the form: C_m(fF) = (3.28 ± 0.63)e^{(0.127± 0.047)*time(min)}, yielding a time-constant of the decay of around 8 minutes. Error bars represent SEM.