General anaesthetics and their effects on GABA(A) receptor desensitization

1. Intravenous anaesthetics, including propofol and thiopental have at leas t three distinct effects on GABA(A) receptor function. 2. Low concentration s of these drugs enhance the amplitude of currents evoked by sub-saturating concentrations of GABA whereas higher concentrations directly activate the receptor in the absence of GABA. 3. Propofol and some barbiturates also de crease the rate and extent of desensitization as indicated by a prolongatio n in the decay of currents evoked by saturating concentrations of GABA. 4. In contrast, sedative benzodiazepines that lack general anaesthetic propert ies do not directly activate the GABA(A) receptor. 5. In addition, benzodia zepines such as midazolam, have no effect on desensitization when examined in the presence of saturating concentrations of GABA. 6. Here, we discuss t he effects of intravenous general anaesthetic on desensitization of the GAB A(A) receptor. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.