Effects of ketamine and propofol on excitatory and inhibitory synaptic transmissions in hippocampal CA1 of the rat

To reveal the mechanisms of general anesthesia on excitatory and inhibitory synaptic transmissions in the central nervous system, we have examined the effects of ketamine and propofol on synaptic transmissions of Shaffer collateral fiber CA1 pyramidal neurones in hippocampal slices of the rat. Katamine (10^-5 to 3x 10^-3mol/l) decreased both EPSP slopes and PS amplitudes in a dose-dependent manner. On the oter hand propofol (10^-6 5x10^-4 mol/l) decreased PS amplitude remaining EPSP slope unchanged. The effects of ketamine were partially blocked by GABA(A) receptor antagonist bicuculline (10^-4 mol/l), and NMDA receptor antagonist AP5 (10^-6mol/l). We conclude that (A) the inhibitory effects of ketamine on PSs were due to the reduction of EPSPs, (B) the ketamine depression of synaptic transmissions may be due to the modulation of both GABA(A) and NMDA receptors, and (C) that propofol depression of synaptic transmissions may be related to GABA(A) receptor.