Chemosphere 2008 Jul 01;729:1256-9. doi: 10.1016/j.chemosphere.2008.05.002.

Ecotoxicology of narcosis: stereoselectivity and potential target sites.

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The stereoselectivity of certain anesthetics is currently thought to be inconsistent with lipid theories of narcosis. The EC50-values of etomidate enantiomers for tadpole narcosis are now examined as a function of octanol/water partition coefficients, and enhancement factors for predicted over experimental EC50 values are determined from a calibration curve for non-selective narcosis. The unfavored S-(-)-enantiomers of etomidate and two analogues surprisingly still fulfill the Meyer-Overton rule. The R+-enantiomers of etomidate and four structural analogues are up to 34-fold more active than expected. The non-chiral anesthetic, propofol, is 8-fold more active than expected. It is concluded that there may be two pathways to tadpole narcosis: enhanced narcosis involving specific receptor binding sites and non-selective narcosis corresponding to the Meyer-Overton rule and operating on the lipid/protein interface.

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