GABAergic mechanisms in the action of general anesthetics

1. The effects of volatile and intravenous anesthetics were studied on evok ed field potentials in rat hippocampal CA1 neurons in vitro to determine th e role of GABAergic mechanisms in the action of general anesthetics. 2. It was observed that both volatile (halothane, isoflurane, sevoflurane) and in travenous (thiopental, pentobarbital, propofol) anesthetics decreased popul ation spike (PS) amplitudes. 3. Using paired-pulse paradigms, it was reveal ed that volatile agents enhance paired-pulse facilitation (PPF), and intrav enous agents reduce PPF. Use-dependent effects on PS amplitudes were observ ed following application of the intravenous anesthetics, whereas volatile a gents did not show use-dependency. The effects of the intravenous anestheti cs were blocked by the GABA(A) receptor antagonist, bicuculline. 4. It is s uggested that agent specific actions of general anesthetics are a result of differential effects on GABAergic mechanisms that modulate synaptic transm ission. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.