The influence of membrane potential on chloride channels activated by GABA in rat cultured hippocampal neurons.
Chloride currents were activated by a low concentration of GABA (0.5 microM) in neonatal rat hippocampal neurons cultured for up to 14 days. Currents elicited by 0.5 microM GABA in neurons, voltage-clamped using the whole-cell technique with pipettes containing 149 mM Cl-, reversed close to 0 mV whether pipettes contained 144 mM Na+ or 140 mM Cs+, and were blocked by 100 microM bicuculline. Current-voltage curves showed outward rectification. Single channel currents appeared in cell-attached patches when the pipette tip was perfused with pipette solution containing 0.5 microM GABA and disappeared when a solution containing 100 microM bicuculline plus 0.5 microM GABA was injected into the pipette tip. The channels showed outward rectification and, in some patches, had a much lower probability of opening at hyperpolarized potentials. The average chord conductance in 10 patches hyperpolarized by 80 mV was 7.8 +/- 1.6 pS (SEM) compared with a chord conductance of 34.1 +/- 3.5 pS (SEM) in the same patches depolarized by 80 mV. Similar single channel currents were also activated in cell-free, inside-out patches in symmetrical chloride solutions when 0.5 microM GABA was injected into the pipette tip. The channels showed outward rectification similar to that seen in cell-attached patches, and some channels had a lower probability of opening at hyperpolarized potentials. The average chord conductance in 13 patches hyperpolarized by 80 mV was 11.8 +/- 2.3 pS (SEM) compared with 42.1 +/- 3.1 pS (SEM) in the same patches depolarized by 80 mV.
Curmi
J P
JP
John Curtin School of Medical Research, Australian National University, Canberra.
Premkumar
L S
LS
Birnir
B
B
Gage
P W
PW
D000818:Animals; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002478:Cells, Cultured; D018118:Chloride Channels / Q000187:drug effects* / Q000378:metabolism*; D004553:Electric Conductivity; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism*; D008564:Membrane Potentials; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology*
D018118:Chloride Channels; D005680:gamma-Aminobutyric Acid