Determination of delta 9-tetrahydrocannabinol levels in brain tissue using high-performance liquid chromatography with electrochemical detection.

delta 9-Tetrahydrocannabinol (delta 9-THC) is the major psychoactive component of cannabis. To assist in investigating the mechanism(s) of action of delta 9-THC, a convenient method for determining its levels in brain tissue is required. We now describe a method for determining nanogram quantities of delta 9-THC in rat brain tissue. The method employs solvent extraction with methanol-hexane-ethyl acetate, followed by analysis using liquid chromatography with electrochemical detection. Overall recoveries were greater than 80%. The relationship between the peak-height ratio for processed standards extracted in the presence of tissue (delta 9-THC/internal standard) and the amount of delta 9-THC added was shown to be linear within the range of concentrations examined. Quantitative measurements of delta 9-THC in different brain regions following the intravenous administration of delta 9-THC are presented as examples of the applications of this method.