Extracellular ATP increases GABA single-channel open time in cell attached mode. GABAAR channels in the patch membrane underneath the tip of the recording pipette were specifically activated by inclusion of GABA (0.5 μM) in the intra-pipette recording solution at a holding membrane potential of 0 mV. A, Representative current traces revealing that ATP (1 mM) increased the GABA single-channel activity only when it was included through the recording pipette. Bar graphs on the Right summarize the mean open probability ( P
; B) and open times (C) averaged from 5 individual recordings in the absence (Control) and presence of ATP (1 mM) outside the pipette in the bath solution (ATP outside pipette) or inside the pipette by its inclusion in the pipette solution (ATP inside pipette). ** P < 0.01.