Monoacylglycerol lipase (MAGL) and fatty acid amide hydrolase (FAAH) inhibitors exert pre-clinical effects indicative of therapeutic potential (i.e., analgesia). However, the extent to which MAGL and FAAH inhibitors produce unwanted effects remains unclear. Here, FAAH and MAGL inhibition was examined separately and together in a Δ9-tetrahydrocannabinol (Δ9-THC; 5.6 mg/kg i.p.) discrimination assay predictive of subjective effects associated with cannabis use, and the relative contribution of N-arachidonoyl ethanolamine (AEA) and 2-arachidonoylglycerol (2-AG) in the prefrontal cortex, hippocampus, and caudate putamen to those effects was examined. Δ9-THC dose-dependently increased Δ9-THC appropriate responses (ED50 value = 3.1 mg/kg), whereas the FAAH inhibitors PF-3845 and URB597 or a MAGL inhibitor JZL184 alone did not substitute for the Δ9-THC discriminative stimulus. The non-selective FAAH/MAGL inhibitors SA-57 and JZL195 fully substituted for Δ9-THC with ED50 values equal to 2.7 and 21.8 mg/kg, respectively. Full substitution for Δ9-THC also was produced by a combination of JZL184 and PF-3845, but not by a combination of JZL184 and URB597 (i.e., 52% maximum). The CB1 receptor antagonist rimonabant attenuated the discriminative stimulus effects of Δ9-THC, SA-57, JZL195, and the combined effects of JZL184 and PF-3845. Full substitution for the Δ9-THC discriminative stimulus occurred only when both 2-AG and AEA were significantly elevated, and the patterns of increased endocannabinoid content were similar among brain regions. Overall, these results suggest that increasing both endogenous 2-AG and AEA produces qualitatively unique effects (i.e., the subjective effects of cannabis) that are not obtained from increasing either 2-AG or AEA separately.
- The American Society for Pharmacology and Experimental Therapeutics