Effects of ketamine on EPSP and population spike in hippocampal CA1 of the rat

In order to reveal the mechanisms of general anesthesia in the central nervous system, we have examined the effects of ketamine on synaptic transmissions of Shaffer collateral fiber input CA1 pyramidal neurones in hippocampal slices of the rat. Ketamine (10^-5 to 3 x 10^-3 mol/l) decreased both EPSP slopes and PS amplitudes in a dose-dependent manner (ED₅₀s were 8.0 x 10^-4 and 1.1 x 10^-3 mol/l, respectively). The effects were partially blocked by GABA(A) receptor antagonist, bicuculline (10^-4 mol/l). We concluded that the inhibitory effects of ketamine on PSs were due to the reduction of EPSPs, and that the ketamine depression of synaptic transmissions may be at least related to GABA(A) receptor.