A, spontaneous membrane currents recorded with CsCl-based intracellular solution reversed polarity at around 0 mV. Nifedipine (20 μm) was present to inhibit L-type Ca2+ channel activation. B, individual mIPSCs from the terminal in A on an expanded time scale, and the average mIPSC in this terminal (n = 158). C, the mIPSCs and the tonic current were inhibited by the GABAA/GABAC receptor antagonist picrotoxin (50 μm). D, the tonic current alone was inhibited by the GABAC receptor antagonist TPMPA (50 μm). E, the mIPSCs alone were inhibited by the GABAA receptor antagonist bicuculline (50 μm).