Fig. 9.

Kinetics of activation and inactivation of transient current in acutely isolated DCN neurons. A, Transient currents isolated by subtraction (noisy traces) after prepulses to either +20 or −110 mV and best fits of Equation 8 (smooth traces). Activation and inactivation time constants were determined from the fit parameters. The inset shows the onset of the current on an expanded time scale (solid lines) and the fits obtained withk = 3.3, which minimized the error function over all voltages (short dashed lines). B, Theopen circles show the voltage dependence of activation of the steady-state current in A. The solid line is the fit of a Boltzmann function to these data. Thefilled squares show the voltage dependence of activation of the transient (difference) current; the line is the best-fitting Boltzmann function. The filled trianglesshow the inactivation (left abscissa), measured as the peak current for a step to 0 mV in B, as a function of the prepulse voltage. The line is the best-fitting Boltzmann function. C, Time constants determined from the fits to Equation 8 for 16 cells.C₁, Activation time constant as a function of voltage. Activation was fast with slight voltage dependence. The regression line is τ = 0.88 − 0.016 ·V (R = 0.20). The histogram on theright summarizes the time constants across all voltages; most activation time constants were between 0.5 and 2 msec at 22°C.C₂, Inactivation time constants as a function of voltage. Inactivation time constants show slight voltage dependence, with most time constants falling between 10 and 40 msec. The regression line is τ = 20.94 + 0.10 · V(R = 0.11). D, Comparison of activation and inactivation time constants for 11 cells, measured at the estimated half-activation voltage for the transient current in each cell. Cells with fast activation showed fast inactivation, whereas cells with slow activation showed slow inactivation. The regression line is τ_inact = 9.5 + 5.8 · τ_activ(R = 0.78).