Figure 2. Kv currents in TH–GFP cells from CB cultures.

A, the outward K⁺ currents elicited in one typical chemoreceptor cell with the voltage protocol depicted in the bottom of the figure. The region marked by the square was enlarged to show the fit of several tail current traces (from test pulses to −10, 0, +10 and +60 mV) to a bi-exponential function. Voltage pulses were applied every 5 s. B, plot of the current–voltage relationship obtained in this cell by measuring the peak current amplitude at each pulse (•). C, plot of the activation curve (▪) and the rapidly (○) and slowly (•) deactivating tail current amplitudes as a function of the voltage of the test pulse for the same cell shown in A. Activation curve was constructed from the peak current amplitude obtained at the beginning of the repolarizing pulse to −40 mV. The lines show the Boltzmann fits of the experimental data. According to the fit, the maximal amplitude of the activation curve in this cell was 206 pA and the midpoint of activation (V_½) was 1.6 mV. The time constants of the two components are shown in the figure.