The Endocannabinoid 2-Arachidonoylglycerol Produced by Diacylglycerol Lipase α Mediates Retrograde Suppression of Synaptic Transmission

Endocannabinoids are released from postsynaptic neurons and cause retrograde suppression of synaptic transmission. Anandamide and 2-arachidonoylglycerol (2-AG) are regarded as two major endocannabinoids. To determine to what extent 2-AG contributes to retrograde signaling, we generated and analyzed mutant mice lacking either of the two 2-AG synthesizing enzymes diacylglycerol lipase alpha (DGL alpha) and beta (DGL beta). We found that endocannabinoid-mediated retrograde synaptic suppression was totally absent in the cerebellum, hippocampus, and striatum of DGL alpha knockout mice, whereas the retrograde suppression was intact in DGL beta knockout brains. The basal 2-AG content was markedly reduced and stimulus-induced elevation of 2-AG was absent in DGL alpha knockout brains, whereas the 2-AG content was normal in DGL beta knockout brains. Morphology of the brain and expression of molecules required for 2-AG production other than DGLs were normal in the two knockout mice. We conclude that 2-AG produced by DGL alpha, but not by DGL beta, mediates retrograde suppression at central synapses.