Voltage-clamp analysis of halothane effects on GABAA fast and GABAA slow inhibitory currents

Voltage-clamped GABA_{A fast} and GABA_{A slow} inhibitory postsynaptic currents (IPSCs) were selectively elicited in hippocampal area CA1 pyramidal neurons. Clinically relevant concentrations of halothane (1.2 vol.%) prolonged both GABA_{A fast} and GABA_{A slow} IPSC decay times approximately 2.5 fold, while having little to no effect on current amplitudes or rise times. Current–voltage analysis revealed that IPSC reversal potentials (−70 to −75 mV) remained constant in the presence of halothane. Under control conditions, GABA_{A slow} IPSC decay times increased linearly with membrane depolarization, and this IPSC decay time voltage dependence was not significantly altered by halothane. These results confirm the existence of separable GABA_{A fast} and GABA_{A slow} IPSCs in hippocampus, and further elucidate the effects of halothane on these currents.