A, superimposed membrane currents elicited with 1·5 s potential steps to -120 mV from a holding potential of -20 mV (pulse interval, 20 s) in 150 mM K+ external solution: control current (a), current about 4 min after continuous application of 1 μM TRH (b) and current after application of 10 μM E-4031 in the continued presence of TRH (c). Recordings were made in the same cell in the whole-cell configuration. B, the current denoted a - c was obtained after subtraction of the current recorded in the presence of E-4031 + TRH (c) from the control current (a), and the TRH-sensitive current (a - b) was obtained after subtraction of the current recorded in the presence of TRH (b) from the control current (a).