| Abstract: | γ‐ Aminobutyric acid is the principal inhibitory neurotransmitter in the central nervous system and regulates the neuronal excitability. There has been anecdotal evidence that γ‐ aminobutyric acid has been used within a few hours prior to competition in equine sports to calm down nervous horses. However, regulating the use of γ‐ aminobutyric acid is challenging because it is an endogenous substance in the horse. γ‐Aminobutyric acid is usually present at low ng/mL levels in equine plasma; therefore, a sensitive method has to be developed to quantify these low background levels. Measuring low concentrations of endogenous γ‐ aminobutyric acid is essential to establish a threshold that can be used to differentiate levels attributable to exogenous administrations of γ‐ aminobutyric acid. A hydrophilic interaction liquid chromatography coupled with tandem mass spectrometry method was developed and validated for the quantitation of γ‐ aminobutyric acid in equine plasma. Calibrators were prepared in artificial surrogate matrix consisting of 35 mg/mL equine serum albumin in phosphate buffered saline. Samples were prepared by protein precipitation with acetonitrile. Utilizing this methodology, a total of 403 equine plasma samples collected post‐competition from horses participating in equestrian events in Canada were analyzed. |
