Blockade by the neutral drug benzocaine. (A) A benzocaine concentration response curve was generated with various benzocaine concentrations (30 µM, 100 µM, 300 µM, 1 mM, and 3 mM). The potency of benzocaine is weaker than lidocaine with an IC50 of 650 µM. Representative traces were obtained from 0 µM, 300 µM, 1 mM, and 3 mM benzocaine applications and are shown in the bottom inset. The dashed line indicates the zero current level. The top inset is a chemical structure of benzocaine. Bar, 500 ms. (B) 3 mM benzocaine was applied extracellularly for 3 min while holding the cells at −120 mV. Test pulse delivery and washout were performed as described in Fig. 2 C. Representative current traces are shown with the zero current lines (dotted lines). Bar, 500 ms. (C) Conductance-voltage relationship curves were generated for control (●) and for after 3 mM benzocaine (○). Similarly, SSI curves were constructed before (■) and after the exposure to 3 mM benzocaine (□). (A–C) n = 4. Error bars represent SEM.
