title: A gas chromatographic-mass spectral assay for the quantitative determination of oleamide in biological fluids.
abstract: Oleamide is a putative endogenous sleep-inducing lipid which potently enhances currents mediated by GABAA and serotonin receptors. While a quantitative assay would aid in determining the role of oleamide in physiological processes, most of the available assays are lacking in sensitivity. We now describe a quantitative assay for measuring low nanogram amounts of oleamide in biological fluids using GC/MS in the selective ion-monitoring mode. The internal standard (13C18 oleamide) was added to known concentrations of oleamide, which were converted to the N-trimethylsilyl or N-tert-butyldimethylsilyl derivatives before analysis by GC/MS, yielding linear calibration curves over the range of 1-25 ng of oleamide when monitoring the m/z 338/356 fragments. Using this technique, oleamide levels were determined following solvent extraction of normal rat cerebrospinal fluid and plasma to be 44 and 9.9 ng/ml, respectively. This technique constitutes a sensitive and reliable method for determining low nanogram quantities of oleamide in biological fluids.
mesh_terms: D000818:Animals; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods*; D008297:Male; D009829:Oleic Acids / Q000032:analysis* / Q000097:blood / Q000134:cerebrospinal fluid; D051381:Rats; D017207:Rats, Sprague-Dawley; D012680:Sensitivity and Specificity