A) Diagram to scale of the two-pulse protocol used to inactivate the L-type Ca current at each of 15 potentials and then the test potential (+20 mV) to measure the remaining non-inactivated current

Copyright information:Taken from "Modulation of L-type Ca current but not activation of Ca release by the gamma subunit of the dihydropyridine receptor of skeletal muscle"BMC Physiology 2001;1():8-8.Published online 24 Jul 2001PMCID:PMC37314.Copyright © 2001 Ahern et al; licensee BioMed Central Ltd. Verbatim copying and redistribution of this article are permitted in any medium for any non-commercial purpose, provided this notice is preserved along with the article's original URL. For commercial use, contact info@biomedcentral.com Ca currents during the pre-pulse and test-pulse phases of the protocol are shown for a pre-pulse depolarization to -70 mV (trace 1), +30 mV (trace 2) and +60 mV (trace 3) in a control, a γ het, and a γ null myotube. The cell capacitance was 317 pF for the control, 175 pF for the γ het and 348 pF for the γ null cell. B) The maximum Ca current during the test pulse is plotted as a function of the pre-pulse potential for 6 control, 8 γ het and 8 γ null cells. C) The non-activating component was subtracted and the curves were normalized to show the voltage-dependence of the inactivating component. I is the maximum test current, Imin is the test current at +50 mV and Imax is the test current at -70 mV. The curves correspond to a Boltzmann fit of the population mean with the following parameters. [(I-Imin)/Imax] = 1, V = -3.8 mV and k = 8.4 mV for control cells. [(I-Imin)/Imax] = 1, V = +15.6 mV and k = 8.1 mV for γ het cells. [(I-Imin)/Imax] = 1, V = +9.7 mV and k = 7.9 mV for γ null cells.