Figure 9. Single-channel conductance of T- and R-type Ca²⁺ channels in adult spiral ganglion neurons.

A Representative and consecutive single-channel traces recorded in a cell-attached patch with pipette solution containing 50 mM Ba²⁺. Additionally, the patch-pipette and bath solution consisted of a cocktail of Ca²⁺ channel blockers; 10 μM nimodipine, 1 μM conotoxin MVIIA, 200 nM ω-(rSNX-482) and 1 μM ω-agatoxin IVA. The holding potential was −90 mV and the step potentials are indicated. B To examine the unitary current fluctuations of R-type Ca²⁺ channels, we included a cocktail of Ca²⁺ channel blockers containing: 10 μM nimodipine, 1 μM conotoxin MVIIA, 5 μM mibefradil and 1 μM ω-agatoxin IVA in the bath and pipette solutions. Shown are sets of families of consecutive single-channel sweeps recorded in the cell-attached configuration, using 50 mM Ba²⁺ as the charge carrier. The membrane patch was held at a holding potential of −70 mV and stepped to potentials denoted above each set of sweeps. C The I V relationships are shown for T and R-type unitary currents, respectively. The single-channel conductances were: T-type 9.5 ± 1.3 pS (n = 5) and R-type channels 14.9 ± 2.8 pS (n = 6).