- 1We performed patch-clamp recordings on acutely isolated somata and dendritic segments of rat neocortical neurons, in order to compare the reversal potential (EGABA) and relative density of GABAA receptor-mediated Cl− currents in these two cellular compartments.
- 2Currents were recorded with the Cl−-impermeable pore former gramicidin (25-75 μg ml−1) in HCO3−-free bath solution. Voltage ramps (-110 to −30 mV) from a holding potential (Vh) of −60 mV in the absence and presence of 2 μM GABA were used to construct instantaneous current-voltage relationships. Currents were abolished by co-application of GABA with the GABAA receptor antagonist bicuculline (40 μM).
- 3GABA conductance, normalized to membrane surface area, was not different in somata and dendrites. In addition, EGABA was not different in the two compartments.
- 4Replacement of intracellular K+ with Cs+ resulted in a significantly more depolarized EGABA in both somata and dendrites. These results suggest that the resting intracellular Cl− concentration ([Cl−]i) is similar in somata and dendrites and that an outward Cl− transporter system maintains low [Cl−]i.