Voltage-clamp analysis of halothane effects on GABA(A fast) and GABA(A 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.