Figure 3. Reversal potential of GABA-evoked responses.

Aa, under voltage clamp, currents evoked by rapid application of GABA (2 μm) over the soma of a functional petrosal neurone in co-culture (I_GABA) at different holding potentials. The functional neurone was first identified by the presence of a depolarizing response to hypoxia (not shown). Ab, corresponding I–V plot shows a reversal potential of approximately −38 mV for I_GABA. In Ba and b, GABA-evoked responses for the same functional neurone were examined under current clamp conditions in the presence of TTX (1 μm) and TEA (5 mm) to block voltage-gated Na⁺ and K⁺ channels, respectively. Changes in membrane potential due to GABA application were measured at different holding potentials (Ba). Note similar reversal potential under these conditions. Both recordings were obtained using gramicidin perforated-patch technique and Hepes-buffered extracellular medium. Membrane potentials have been corrected for liquid junction potential of 9 mV between patch pipette and bath solution.