Butanol Isomers Exert Distinct Effects on Voltage-Gated Calcium Channel Currents and Thus Catecholamine Secretion in Adrenal Chromaffin Cells
Figure 6
1-butanol and tert-butanol produce a similar hyperpolarization of closed-state inactivation.
A) Schematic depiction of the voltage-stimulus protocol. ICa were elicited by steps to +10 mV. The holding potential was increased in 10 mV increments from −90 mV to −20 mV and maintained at each potential for 30 s. In each cell this was done first in control conditions and then in the presence of either 1-butanol (panel B; n = 5) or tert-butanol (panel C; n = 6). B, C) ICa amplitude was normalized to that evoked from a holding potential of −90 mV and plotted against the holding potential. The graphs show the mean data fit using a Boltzmann function with three free parameters (upper plateau, slope, and V50) and the lower plateau was constrained to ≥0. The inset bar graphs show the hyperpolarizing shift in mean V50 (voltage at half maximal inactivation) derived from the Boltzmann fits to individual cells (** p<0.01; *** p<0.001 compared to matched controls; paired t-test).