GABA activates single-channel currents in a graded manner and the currents are inhibited by flumazenil.

<p><b>A</b>. 10 nM GABA-activated channels in a cell-attached (ca) patch that was then ripped-off the cell and an inside-out (io) patch formed (−Vp = 40 mV). <b>a</b>, In a reversible manner 1 µM flumazenil inhibits the GABA-activated current. <b>b</b>, 30 s (i, ii, iv) and 3.5 min (iii) all-points open probability histograms <b>c</b>, Currents from the trace shown in <b>a</b> (*) <b>B</b>. Average IV relation, currents activated by 10 nM GABA in ca (○, open circle, n = 5–18), io (▽, open triangle, n = 3–6) patches. ▴, filled triangle, an io patch were currents were later inhibited by 1 µM flumazenil. <b>C</b>. GABA-activated currents in ca patches (−Vp = 40 mV) and 10 s all-points open probability histograms. 0.01, 0.1, 1 and 1000 nM GABA activated 0.6, 1.3, 2.2 and 2.0 pA channels, respectively. All patches were later made io and currents inhibited by 1 µM flumazenil. <b>D</b>. Conductance-GABA concentration relation, 52 ca patches, −Vp = 40 mV. •, patches later made io and currents blocked with 1 µM flumazenil. E. 10 pM GABA-activated channels in a ca patch that was then ripped-off the cell and an io patch formed (−Vp = 40 mV). The recordings are from the io patch in 10 pM GABA in the absence and presence of 1 µM flumazenil and the all-points histograms are each from a 10 s current trace that includes the sample trace shown.