GABAergic mechanisms in the action of general anesthetics.

1. The effects of volatile and intravenous anesthetics were studied on evoked field potentials in rat hippocampal CA1 neurons in vitro to determine the role of GABAergic mechanisms in the action of general anesthetics. 2. It was observed that both volatile (halothane, isoflurane, sevoflurane) and intravenous (thiopental, pentobarbital, propofol) anesthetics decreased population spike (PS) amplitudes. 3. Using paired-pulse paradigms, it was revealed that volatile agents enhance paired-pulse facilitation (PPF), and intravenous agents reduce PPF. Use-dependent effects on PS amplitudes were observed following application of the intravenous anesthetics, whereas volatile agents did not show use-dependency. The effects of the intravenous anesthetics were blocked by the GABA(A) receptor antagonist, bicuculline. 4. It is suggested that agent specific actions of general anesthetics are a result of differential effects on GABAergic mechanisms that modulate synaptic transmission.