Fig. 1

Competitive gel-based ABPP reveals higher FAAH over MAGL activity in rat meninges and LC–MS/MS shows 2-AG as the main meningeal endoCB. A Rat meninges were pre-incubated for 1 h with DMSO (vehicle), MAGL-inhibitors JJKK-048 (100 nM) and KML-29 (1 μM) and FAAH-inhibitors JZP-327A (1 μM) and JZP-430 (1 μM), and then labelled with fluorescent probe TAMRA-FP, as indicated in the Methods. TAMRA-FP-labelled bands appear dark after in-gel imaging. FAAH and MAGL were identified based on selective inhibition and their expected molecular weights. MAGL and FAAH band-intensities after DMSO treatment represent basal MAGL and FAAH activities, respectively. Note that FAAH activity after DMSO treatment is high, whereas basal MAGL activity is practically absent. Basal FAAH- activity was reduced with JZP-327A (N = 6, Friedman test) and with JZP-430 (N = 6, Friedman test). MAGL-inhibitors JJKK-048 (100 nM) and KML-29 (1 μM) did not affect FAAH basal activity. B Statistics comparing the basal activity of MAGL and FAAH in rat meninges. Basal FAAH activity was higher than MAGL activity (N = 6, Mann Whitney U test, ** = 0.002). C LC–MS/MS data comparing AEA and 2-AG levels in naïve rat meninges. The level of 2-AG was much higher than that of AEA (N = 5, Mann Whitney U test, ** = 0.002). D LC–MS/MS data comparing AEA levels in naïve rat meninges vs. after 4 h incubation of 100 mM KCl pro-nociceptive treatment. KCl treatment significantly increased AEA levels compared to its basal level (N = 5, Mann Whitney U test, * = 0.033). E LC–MS/MS data comparing 2-AG levels in naïve rat meninges (N=5) vs. after a 4-h 100-mM KCl pro-nociceptive treatment (N=4). No significant differences in 2-AG levels were detected (Mann Whitney U test)