Direct observation of a fluorinated anticonvulsant in brain tissue using 19F-NMR techniques.
A fluorinated derivative of an anticonvulsant gamma-butyrolactone [alpha-(1,1-difluoroethyl)-alpha-methyl-gamma-butyrolactone; alpha-DFGBL] was synthesized as a probe for NMR spectroscopic observation of the drug in brain tissue. The fluorinated compound is an efficacious anticonvulsant in mice, and inhibits the specific binding of [35S]t-butylbicyclophosphorothionate ([35S]TBPS) to mouse brain membranes with a concentration dependence similar to that of the non-fluorinated compound alpha-ethyl-alpha-methyl-gamma-butyrolactone. Quantitative 19F-NMR spectroscopic studies, coupled with chromatographic measurements of drug tissue concentration, showed that virtually all of the alpha-DFGBL in brain was NMR-observable and that, following intraperitoneal injection, alpha-DFGBL rapidly achieved millimolar concentrations in brain. The 19F-NMR spectra of a alpha-DFGBL in brain and liver tissue were broad (1-2 ppm) and complex, exhibiting multiple chemical shift features. The major chemical shift features in these spectra were assigned on the basis of differential extraction and comparison of 19F spin-spin relaxation times (T2s) and 19F chemical shifts of alpha-DFGBL in tissue to those in pure solvents. The major feature at 10.4 ppm in the tissue spectra was assigned to a weakly polar, membrane-associated environment for the fluorinated compound, while the feature at 11.2 ppm was assigned to an aqueous environment for alpha-DFGBL. The drug was in slow exchange between these two environments in brain. In addition, the feature at lowest field (9.7-9.8 ppm) was identified as a water-soluble hydroxy-acid metabolite of alpha-DFGBL produced by the liver. These data indicate that gamma-butyrolactone anticonvulsants achieve high concentrations in brain, where they exist in several, largely membrane-associated, environments. These findings are consistent with the purported action of the gamma-butyrolactones as low-affinity modulators of gamma-aminobutyric acid-A channels.
Canney
D J
DJ
Department of Molecular Biology, Washington University School of Medicine, St. Louis, MO 63110.
Covey
D F
DF
Evers
A S
AS
D015107:4-Butyrolactone / Q000031:analogs & derivatives* / Q000032:analysis / Q000138:chemical synthesis / Q000493:pharmacokinetics; D000273:Adipose Tissue / Q000737:chemistry; D000818:Animals; D000927:Anticonvulsants / Q000032:analysis*; D001921:Brain / Q000378:metabolism; D001923:Brain Chemistry; D001643:Bridged Bicyclo Compounds / Q000378:metabolism; D019086:Bridged Bicyclo Compounds, Heterocyclic; D002849:Chromatography, Gas; D003292:Convulsants / Q000378:metabolism; D008099:Liver / Q000737:chemistry / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D051379:Mice; D014018:Tissue Distribution
D000927:Anticonvulsants; D001643:Bridged Bicyclo Compounds; D019086:Bridged Bicyclo Compounds, Heterocyclic; D003292:Convulsants; C080278:alpha-(1,1,-difluoroethyl)-alpha-methyl-gamma-butyrolactone; C037476:tert-butylbicyclophosphorothionate; D015107:4-Butyrolactone