LIDOCAINE HAS DIFFERENT EFFECTS AND POTENCIES ON MUSCLE AND BRAIN SODIUM-CHANNELS

Lidocaine effects were studied at the single channel level on batracho toxin-activated eel electroplax (muscle-derived) and on rat brain sodi um channels in planar lipid bilayers to investigate whether these effe cts were the same on structurally different sodium channels. Lidocaine blocked the open state of brain channels with the same voltage depend ence, but with 15-times as high a potency as muscle-derived channels. In brain channels, but not muscle-derived ones, the lever of the open channel block showed periods of relief. Lidocaine at mu M concentratio ns stabilized the highest conductance state in both channel types and at mM concentrations stabilized subconductance-like states in electrop lax, but not in brain channels. In both channel types, lidocaine incre ased the lifetime and rate of entry to a long-nonconducting state. Sin ce both channel types were studied under identical lipid and ionic con ditions, the observed functional differences in the lidocaine action ( effects, potency) must reflect channel structural differences.