Figure 6.

Inhibitory effects of quinine (a, b) and La³⁺ (c, d) on carbachol-induced whole-cell and single channel currents measured at −40 mV. Whole-cell (top panel) and single channel (bottom panel) currents were reversibly suppressed by the bath application of 20 μM quinine. Single channel conductance was unaltered while channel NP_o decreased from 0.18 to 0.03 (b). Bath application of 2 mM La³⁺ caused a rapid inhibition of both whole-cell (c top panel) and single channel (c bottom panel) currents. The latter were inhibited mainly via a reduction of the unitary current amplitude (top panel in d, squares and circles show the open channel I–V relationships before and after 2 mM La³⁺ application, respectively; n=3) as well as variable reduction in NP_o (bottom panel in d). No single channel activity was observed at positive potentials in the presence of La³⁺.