title: Differential alteration of hippocampal excitatory synaptic transmission by cannabinoid ligands.
abstract: Cannabinoid compounds affect synaptic activity and plasticity in numerous brain areas by activating CB1 receptors (CB1). In hippocampus, varying results have been obtained on the extent and site of cannabinoid actions on excitatory transmission, ranging from no effect to complete obliteration of synaptic responses. Here we used the rat hippocampal slice preparation to study and compare the effect of various synthetic and endogenous CB1 ligands on excitatory synaptic transmission. The full CB1 agonist WIN55212-2 (WIN2) greatly decreased excitatory synaptic transmission by 62%. The effect of WIN-2 was concentration dependent (EC50 of 200 nM) and completely prevented by CB1 antagonists. The nondegradable partial CB1 agonist R1-methanandamide (mAEA) decreased transmission by 25% and the endocannabinoids 2-arachidonylglycerol (2-AG) and anandamide (AEA) had no significant effect. The action of AEA was improved by inhibiting its degradation but not its transport. The effect of 2-AG was enhanced upon inhibition of COX-2 but remained unchanged with blockade of monoacylglycerol lipase (MAGL). The observed effects were prevented by CB1 antagonists regardless of the ligand used, and paired-pulse paradigms pointed to presynaptic mechanisms of cannabinoid action. Our results show that cannabinoid effects on neuronal activity differ widely according to the CB1 ligand used. We observed large differences between full (synthetic) and partial (endogenous) CB1 agonists in altering synaptic transmission, notably because of the involvement of active degradation mechanisms.
authors.affiliation: Molecular and Integrative Neurosciences Department, The Scripps Research Institute, La Jolla, California 92037, USA.
authors.forename: Michal
authors.initials: M
authors.lastname: Bajo
authors.forename: Marisa
authors.initials: M
authors.lastname: Roberto
authors.forename: Paul
authors.initials: P
authors.lastname: Schweitzer
mesh_terms: D000818:Animals; D001095:Arachidonic Acids / Q000494:pharmacology; D048588:Benzoxazines / Q000494:pharmacology; D051546:Cyclooxygenase 2 / Q000378:metabolism; D052246:Cyclooxygenase 2 Inhibitors / Q000494:pharmacology; D004558:Electric Stimulation; D063388:Endocannabinoids; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects; D005989:Glycerides / Q000494:pharmacology; D006624:Hippocampus / Q000187:drug effects / Q000502:physiology*; D066298:In Vitro Techniques; D008024:Ligands; D008297:Male; D008994:Monoacylglycerol Lipases / Q000378:metabolism; D009025:Morpholines / Q000494:pharmacology; D009281:Naphthalenes / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects / Q000502:physiology / Q000648:ultrastructure; D018408:Patch-Clamp Techniques; D053284:Polyunsaturated Alkamides / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D043884:Receptor, Cannabinoid, CB1 / Q000819:agonists / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology*
chemical_list: D001095:Arachidonic Acids; D048588:Benzoxazines; D052246:Cyclooxygenase 2 Inhibitors; D063388:Endocannabinoids; D005989:Glycerides; D008024:Ligands; D009025:Morpholines; D009281:Naphthalenes; D053284:Polyunsaturated Alkamides; D043884:Receptor, Cannabinoid, CB1; C088155:methanandamide; C070417:(3R)-((2,3-dihydro-5-methyl-3-((4-morpholinyl)methyl)pyrrolo-(1,2,3-de)-1,4-benzoxazin-6-yl)(1-naphthalenyl))methanone; C094503:glyceryl 2-arachidonate; D051546:Cyclooxygenase 2; C489691:Ptgs2 protein, rat; D008994:Monoacylglycerol Lipases; C078814:anandamide