title: Additive effects of sevoflurane and propofol on gamma-aminobutyric acid receptor function.
abstract: BACKGROUND
  Previous studies have shown that propofol and sevoflurane enhance the function of gamma-aminobutyric acid type A (GABAA) receptors. However, it is not known whether these two drugs modulate the same molecular pathways. In addition, little is known about receptor function in the presence of both propofol and sevoflurane. The aim of this study was to better understand the interactions of propofol and sevoflurane with the GABAA receptor.
  
  
  METHODS
  Wild-type alpha1, beta(2), gamma(2s) GABA(A) receptor subunit complementary DNAs were transfected into human embryonic kidney cells grown on glass coverslips using a calcium phosphate transfection method. After transfection (36-72 h), cells were whole cell patch clamped and exposed to combinations of the following: 0.3-1,000 microm gamma-aminobutyric acid (GABA), 0-10 microm propofol, and 0-1,650 microm sevoflurane. Chemicals were delivered to the cells using two 10-channel infusion pumps and a rapid solution exchanger.
  
  
  RESULTS
  Both propofol and sevoflurane alone enhanced the amplitude of GABA(A) receptor responses to submaximal concentrations of GABA in a dose-dependent manner. The enhancement was underpinned by an increase in the apparent affinity of the receptor for GABA. Coapplication of both anesthetics further enhanced the apparent affinity of the receptor for GABA.
  
  
  CONCLUSIONS
  Response surface modeling of the potentiation of GABA responses (0.3-1,000 microm) by sevoflurane and propofol revealed that the two anesthetics modulated receptor function in an additive manner. These results are consistent with recent mutagenesis studies, suggesting that these two drugs have separate binding sites and converging pathways of action on the GABAA receptor.
authors.affiliation: Department of Physics, Emory College, Atlanta, Georgia 30322, USA.
authors.forename: Luke E
authors.initials: LE
authors.lastname: Sebel
authors.forename: James E
authors.initials: JE
authors.lastname: Richardson
authors.forename: Sunil P
authors.initials: SP
authors.lastname: Singh
authors.forename: Shannon V
authors.initials: SV
authors.lastname: Bell
authors.forename: Andrew
authors.initials: A
authors.lastname: Jenkins
mesh_terms: D000768:Anesthesia, General; D000777:Anesthetics / Q000494:pharmacology*; D004357:Drug Synergism; D006801:Humans; D008738:Methyl Ethers / Q000494:pharmacology*; D015742:Propofol / Q000494:pharmacology*; D011963:Receptors, GABA-A / Q000187:drug effects* / Q000502:physiology; D000077149:Sevoflurane; D014162:Transfection; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology
chemical_list: D000777:Anesthetics; D008738:Methyl Ethers; D011963:Receptors, GABA-A; D000077149:Sevoflurane; D005680:gamma-Aminobutyric Acid; D015742:Propofol