Single channel properties of outwardly rectifying chloride currents in CA1 pyramidal neurons of adult rat hippocampus

An outwardly rectifying chloride channel (ORCC) was characterized in acutely dissociated hippocampal CA1 pyramidal neurons of adult rat by using inside-out configuration of patch clamp. The channels were usually activated by a long-lasting and depolarizing voltage step. Average single channel conductance was (16.58 +/- 1.54) pS for membrane potential between -60 mV and 0 mV, and (40.92 +/- 3.17) pS between 0 mV and + 60 mV in symmetrical 150 mmol/L NaCl solution (n = 10). The channel open probability was voltage dependent (V-m = -60 mV, P-o = 0.44 +/- 0.12; V-m = + 60 mV, P-o = 0. 86 +/- 0. 06, n = 10). The reversal potential of the channel was (-4.17 +/- 1.84) mV in symmetrical Cl- concentration (150 mmol/L). When partially substituting Na-Gluconate for NaCl, the reversal potential shifted to (-34.23 +/- 4.86) mV ([Cl-](i)/ [Cl- ](o) = (30 mmol/L) / (150 mmol/L)). This shift indicates a high Cl- selectivity of the channel. Chloride channel blockers DIDS and SITS showed a reversible inhibiting effect on the channel activity. These results provide a report of an outwardly rectifying chloride channel (ORCC) in hippocampal CA1 pyramidal neurons of adult rat.