title: Acute inhibition of diacylglycerol lipase blocks endocannabinoid-mediated retrograde signalling: evidence for on-demand biosynthesis of 2-arachidonoylglycerol.
abstract: The endocannabinoid (eCB) 2-arachidonoylglycerol (2-AG) produced by diacylglycerol lipase α (DGLα) is one of the best-characterized retrograde messengers at central synapses. It has been thought that 2-AG is produced 'on demand' upon activation of postsynaptic neurons. However, recent studies propose that 2-AG is pre-synthesized by DGLα and stored in neurons, and that 2-AG is released from such 'pre-formed pools' without the participation of DGLα. To address whether the 2-AG source for retrograde signalling is the on-demand biosynthesis by DGLα or the mobilization from pre-formed pools, we examined the effects of acute pharmacological inhibition of DGL by a novel potent DGL inhibitor, OMDM-188, on retrograde eCB signalling triggered by Ca(2+) elevation, Gq/11 protein-coupled receptor activation or synergy of these two stimuli in postsynaptic neurons. We found that pretreatment for 1 h with OMDM-188 effectively blocked depolarization-induced suppression of inhibition (DSI), a purely Ca(2+)-dependent form of eCB signalling, in slices from the hippocampus, striatum and cerebellum. We also found that at parallel fibre-Purkinje cell synapses in the cerebellum OMDM-188 abolished synaptically induced retrograde eCB signalling, which is known to be caused by the synergy of postsynaptic Ca(2+) elevation and group I metabotropic glutamate receptor (I-mGluR) activation. Moreover, brief OMDM-188 treatments for several minutes were sufficient to suppress both DSI and the I-mGluR-induced retrograde eCB signalling in cultured hippocampal neurons. These results are consistent with the hypothesis that 2-AG for synaptic retrograde signalling is supplied as a result of on-demand biosynthesis by DGLα rather than mobilization from presumptive pre-formed pools.
authors.affiliation: M. Kano: Department of Neurophysiology, Graduate School of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan. mkano-tky@m.u-tokyo.ac.jp.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Hashimotodani
authors.forename: Takako
authors.initials: T
authors.lastname: Ohno-Shosaku
authors.forename: Asami
authors.initials: A
authors.lastname: Tanimura
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Kita
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Sano
authors.forename: Takao
authors.initials: T
authors.lastname: Shimizu
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Di Marzo
authors.forename: Masanobu
authors.initials: M
authors.lastname: Kano
mesh_terms: D000818:Animals; D001095:Arachidonic Acids / Q000096:biosynthesis*; D001921:Brain / Q000166:cytology / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D063388:Endocannabinoids / Q000096:biosynthesis*; D043802:GTP-Binding Protein alpha Subunits, Gq-G11 / Q000378:metabolism; D005989:Glycerides / Q000096:biosynthesis*; D007532:Isoleucine / Q000031:analogs & derivatives / Q000494:pharmacology; D007783:Lactones / Q000494:pharmacology; D008071:Lipoprotein Lipase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D011689:Purkinje Cells / Q000378:metabolism / Q000502:physiology; D018094:Receptors, Metabotropic Glutamate / Q000378:metabolism; D013569:Synapses / Q000378:metabolism / Q000502:physiology; D009435:Synaptic Transmission
chemical_list: D001095:Arachidonic Acids; D063388:Endocannabinoids; D005989:Glycerides; D007783:Lactones; C585831:N-formyl-isoleucine-1-((3-hexyl-4-oxo-2-oxetanyl)methyl)dodecyl ester; D018094:Receptors, Metabotropic Glutamate; D007532:Isoleucine; C094503:glyceryl 2-arachidonate; D008071:Lipoprotein Lipase; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D002118:Calcium