Fig. 3. Voltage dependence of time-to-peak (A) and inactivation time constant (; B) of the low-voltage-activated calcium current. Sr²⁺ was used as the charge carrier. The stimulus protocol for both graphs was a series of 25 ms test pulses with increments of 10 mV from -70 to +90 mV from a holding potential of -80 mV. The time constant () for the inactivation decay was obtained by fitting the calcium current decay with a single exponent at each testing potential using the Clampfit program (Axon Instruments). The means from each testing potential were fitted with Sigma Plot 4.0 program (SPSS Inc.). Values are means ± S.E.M., N=10 cells.