Quantitative measurement of depolarization-induced anandamide release in human and rat neocortex

It has been suggested that the endocannabinoid anandamide is released from central neurons upon depolarization of the cell membrane. In order to determine whether anandamide levels were increased after K(+) depolarization of fresh human and rat brain slices, we developed a rapid and sensitive method for the isolation and quantitation of anandamide. This included solvent extraction, solid phase separation, and reversed phase high performance liquid chromatography (HPLC) with fluorometric detection. Compared with basal levels, K(+) stimulation enhanced the neocortical anandamide concentration in both species (70.5 vs. 21.1 pmol/g tissue in humans, 14.3 vs. 3.2 pmol/g tissue in rats). Basal anandamide levels in the rat hippocampus (11.1 pmol/g) were significantly higher than in the neocortex. Anandamide was also detected in the human amygdala (67.8 pmol/g). In conclusion, our data provide evidence for the depolarization-induced synthesis of anandamide, supporting the hypothesis of a neuromodulatory action of this endocannabinoid. Furthermore, the presence of anandamide in the limbic system suggests participation in cognition, behavior or reward.