Figure 5
Intracellular free Na+ does not block Ca v 2.3 channels expressed alone or co-expressed with SmCa v β or Ca v β 2a but induces SmCa v β-dependent run-down of Ca v 2.3 currents. Current-voltage relationships from HEK cells expressing Cav2.3 subunits alone (A), co-expressing Cav2.3 and SmCavβ subunits (B) or co-expressing Cav2.3 and Cavβ2a subunits (C) in minimal intracellular solution (filled circles) and in intracellular solution containing 5 mM NaCl (open circles). Peak currents generated by voltage steps from -20 mV to +75 mV in 5 mV steps from a holding potential of -80 mV are plotted. Data points represent mean ± s.e.m. (D) Peak current amplitude in the presence of 5 mM internal NaCl relative to peak current amplitude in the absence of NaCl for Cav2.3 subunits alone, co-expressed with SmCavβ subunits or co-expressed with Cavβ2a subunits. (E) Relative current amplitude of currents produced by Cav2.3 (filled circles) channels alone and in combination with SmCavβ (open circles) plotted as a function of time in the presence of 5 mM NaCl in the patch-pipette solution. Values are means ± s.e.m, N = 3 – 9.