Determination of the EC50 amnesic concentration of etomidate and its diffusion profile in brain tissue: implications for in vitro studies.

Determination of the EC50 amnesic concentration of etomidate and its diffusion profile in brain tissue: implications for in vitro studies. Research Abstract Details 

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Determination of the EC50 amnesic concentration of etomidate and its diffusion profile in brain tissue: implications for in vitro studies. Abstract Text:

Claudia Benkwitz,Mark Liao,Michael J Laster,James M Sonner,Edmond I Eger,Robert A Pearce,

BACKGROUND: Etomidate is a widely used general anesthetic that has become a useful tool to investigate mechanisms of anesthetic action in vivo and in brain slices. However, the free aqueous concentration of etomidate that corresponds to amnesia in vivo and the diffusion profile of etomidate in brain slices are not known. METHODS: The authors assessed the effect of intraperitoneally injected etomidate on contextual fear conditioning in mice. Etomidate concentrations in brain tissue were obtained by high-performance liquid chromatography. Uptake studies in 400-microm-thick brain slices were used to calculate the diffusion and partition coefficients of etomidate. A diffusion model was used to calculate the expected concentration profile within a brain slice as a function of time and depth. The predicted rate of drug equilibration was compared with the onset of electrophysiologic effects on inhibitory circuit function in recordings from hippocampal brain slices. RESULTS: Etomidate impaired contextual fear conditioning with an ED50 dose of 11.0+/-0.1 mg after intraperitoneal injection, which corresponded to an EC50 brain concentration of 208+/-9 ng/g. The brain:artificial cerebrospinal fluid partition coefficient was 3.35, yielding an EC50,amnesia aqueous concentration of 0.25 microm. The diffusion coefficient was approximately 0.2x10 cm/s. The development of etomidate action in hippocampal brain slices was compatible with the concentration profile predicted by this diffusion coefficient. CONCLUSIONS: The free aqueous concentration of etomidate corresponding to amnesia, as defined by impaired contextual fear conditioning in mice, is 0.25 microM. Diffusion of etomidate into brain slices requires approximately an hour to reach 80% equilibration at a typical recording depth of 100 microm. This information will be useful in designing and interpreting in vitro studies using etomidate.

Determination of the EC50 amnesic concentration of etomidate and its diffusion profile in brain tissue: implications for in vitro studies. Publishing Authors By Initials

C Benkwitz,M Liao,MJ Laster,JM Sonner,EI Eger,RA Pearce,

For similar behavior and behavior mechanisms: behavior: motor activity research abstracts see: behavior and behavior mechanisms: behavior: motor activity research

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Determination of the EC50 amnesic concentration of etomidate and its diffusion profile in brain tissue: implications for in vitro studies. Journal Published:

PUBLICATION TYPE: Research Support, Non-U.S. Gov

Journal: Anesthesiology

VOLUME: 106

Page Numbers: 114-23

Journal Abbreviation: Anesthesiology

ISSN: 0003-3022

DAY: 3

MONTH: Jan

YEAR: 2007

Determination of the EC50 amnesic concentration of etomidate and its diffusion profile in brain tissue: implications for in vitro studies. Information

Number of References:

LANGUAGE: eng

NlmUniqueID: 1300217

Determination of the EC50 amnesic concentration of etomidate and its diffusion profile in brain tissue: implications for in vitro studies. Keywords Mesh Terms:

KEYWORDS: Motor Activity

MESH TERMS: drug effects

Chemical & Substance for Abstract: Determination of the EC50 amnesic concentration of etomidate and its diffusion profile in brain tissue: implications for in vitro studies. Information

Substance Name: Etomidate

Registry Number: 33125-97-2

Grant and Affiliation Information for Determination of the EC50 amnesic concentration of etomidate and its diffusion profile in brain tissue: implications for in vitro studies.

AFFILIATION: Department of Anesthesiology, University of Wisconsin, Madison 53711, USA.

Country: United States

AGENCY: United States NIGMS

GRANT: GM55719

ACRONYM: GM

MEDLINETA: Anesthesiology

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