Figure 2.

Block of GLIC by TEA⁺. (A) Macroscopic current responses to 5-s pulses of pH 4.5 solution (pH_holding 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 TEA⁺ (left), in the presence of 5 mM TEA⁺ flowing through both barrels of the theta-type perfusion tubing (middle), and back again, without TEA⁺ 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 TEA⁺, 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 TEA⁺. 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 5 mM TEA⁺ and upon TEA⁺ removal normalized to the peak value observed in the initial TEA⁺-free recording. (C) Time constants of desensitization during the application of pH 4.5 in the presence of external 5 mM TEA⁺ and upon TEA⁺ removal normalized to the time constant fitted to the initial TEA⁺-free recording. The values plotted in B and C are means obtained from 6 patches; error bars are the corresponding standard errors.