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Tissue levels of anandamide (AEA) and 2-arachidonoylglycerol (2-AG) have been determined in 16 regions and nuclei from human brains, using liquid chromatography/inline mass spectrometry. Measurements in brain samples stored at −80°C for 2 months to 13 years indicated that endocannabinoids were stable under such conditions. In contrast, the postmortal delay had a strong effect on brain endocannabinoid levels, as documented in brain samples microdissected and frozen 1 to 6h postmortem, and in neurosurgical samples 0, 5, 30, 60, 180 and 360 min after their removal from the brain. The tissue levels of AEA increased continuously and in a region-dependent manner from one hour after death, increasing about 7-fold by 6h postmortem. In contrast, concentrations of 2-AG, which were 10 to 100-times higher in human brain regions than those of AEA, rapidly declined: within the first hour, 2-AG levels dropped to 25-35% of the initial ('0 min') value, where after they remained relatively stable. As analyzed in samples removed 1-1.5h post mortem, AEA levels ranged from a high of 96.3 fmol/mg tissue in the nucleus accumbens to a low of 25.0 fmol/ mg in the cerebellum. 2-AG levels varied 8-fold, from 8.6 pmol/mg in the lateral hypothalamus to 1.1 pmol/mg in the nucleus accumbens. Relative levels of AEA and 2-AG varied from region to region, with the 2-AG:AEA ratio being high in the sensory spinal trigeminal nucleus (140:1), the spinal dorsal horn (136:1) and the lateral hypothalamus (98:1) and low in the nucleus accumbens (16:1) and the striatum (31:1). The results highlight the pitfall of analyzing endocannabinoid content in brain samples of variable postmortal delay, and document differential distribution of the two main endocannabinoids in the human brain.

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1. Nucleosides potentially participate in the neuronal functions of the brain. However, their distribution and changes in their concentrations in the human brain is not known. For better understanding of nucleoside functions, changes of nucleoside concentrations by age and a complete map of nucleoside levels in the human brain are actual requirements. 2. We used post mortem human brain samples in the experiments and applied a recently modified HPLC method for the measurement of nucleosides. To estimate concentrations and patterns of nucleosides in alive human brain we used a recently developed reverse extrapolation method and multivariate statistical analyses. 3. We analyzed four nucleosides and three nucleobases in human cerebellar, cerebral cortices and in white matter in young and old adults. Average concentrations of the 308 samples investigated (mean+/-SEM) were the following (pmol/mg wet tissue weight): adenosine 10.3+/-0.6, inosine 69.5+/-1.7, guanosine 13.5+/-0.4, uridine 52.4+/-1.2, uracil 8.4+/-0.3, hypoxanthine 108.6+/-2.0 and xanthine 54.8+/-1.3. We also demonstrated that concentrations of inosine and adenosine in the cerebral cortex and guanosine in the cerebral white matter are age-dependent. 4. Using multivariate statistical analyses and degradation coefficients, we present an uneven regional distribution of nucleosides in the human brain. The methods presented here allow to creation of a nucleoside map of the human brain by measuring the concentration of nucleosides in microdissected tissue samples. Our data support a functional role for nucleosides in the brain.

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