Block of GLIC by lidocaine. (A) Macroscopic current responses to 5-s pulses of pH-4.5 solution (pHholding 7.4) recorded at –80 mV in the outside-out configuration. The response of each patch of membrane was recorded sequentially in the absence of lidocaine (left), in the presence of 0.5 mM lidocaine flowing through both barrels of the theta-type perfusion tubing (middle), and back again, without lidocaine in either barrel (right). The solutions flowing through the two barrels of the perfusion tubing were (in mM) 142 KCl, 5.4 NaCl, 1.8 CaCl2, 1.7 MgCl2 with or without lidocaine, and pH-buffered with 10 mM HEPES/KOH, pH 7.4, or with 10 mM acetic-acid/KOH, pH 4.5. In the schematic representations of the theta-tubing perfusion, arrows indicate the application of lidocaine. Note the expanded current scale used for the middle panel; the trace is the average of 25 consecutive responses recorded from a representative patch. (B) Peak-current amplitudes recorded in response to the application of pH 4.5 in the presence of external 0.5 mM lidocaine and upon lidocaine removal normalized to the peak value observed in the initial lidocaine-free recording. (C) Current-decay time constants during the application of pH 4.5 in the presence of external 0.5 mM lidocaine and upon lidocaine removal normalized to the time constant fitted to the initial lidocaine-free recording. The values plotted in B and C are means obtained from 12 patches; error bars are the corresponding standard errors.
