urb-754 and glyceryl-2-arachidonate

Cerebrovascular smooth muscle cells express the CB1 cannabinoid receptor and CB1 agonists produce vasodilatation of the middle cerebral artery (MCA). The thromboxane A2 mimetic, U-46619, increased the content of the endocannabinoid, 2-arachidonoylglycerol (2-AG) in the MCA and 2-AG moderated the vasoconstriction produced by U46619 in this tissue. The purposes of this study were to examine the extent to which 2-AG is catabolized by cerebral arteries and to determine whether blockade of 2-AG inactivation potentiates its feedback inhibition of U-44619-mediated vasoconstriction.. The diameters of isolated, perfused MCA from male rats were measured using videomicroscopy.. Exogenous 2-AG produces a CB1 receptor-dependent and concentration-related increase in the diameter of MCA constricted with 5-HT. The E (max) for 2-AG dilation is increased 4-fold in the presence of the metabolic inhibitors 3-(decylthio)-1,1,1-trifluropropan-2-one (DETFP), URB754 and URB597. To examine the role of catabolism in the effects of endogenous 2-AG, vasoconstriction induced by U-46619 was studied. DETFP and URB754, but not the fatty acid amide hydrolase inhibitor, URB597, significantly increased the EC(50) for U-46619. These data support a physiological role for endocannabinoid feedback inhibition in the effects of U-46619 and indicate that endogenously produced 2-AG is also efficiently catabolized within the MCA.. MCA express mechanisms for the efficient inactivation of 2-AG, providing further support for an endocannabinoid feedback mechanism that opposes thromboxane-mediated vasoconstriction. These data suggest that potentiation of endogenously produced 2-AG could be a novel therapeutic approach to the treatment of thrombotic stroke.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Amidohydrolases; Aniline Compounds; Animals; Arachidonic Acid; Arachidonic Acids; Benzamides; Benzoxazines; Carbamates; Dose-Response Relationship, Drug; Drug Synergism; Endocannabinoids; Enzyme Inhibitors; Glycerides; In Vitro Techniques; Male; Middle Cerebral Artery; Morpholines; Naphthalenes; Nimodipine; Piperidines; Pyrazoles; Rats; Rats, Sprague-Dawley; Receptor, Cannabinoid, CB1; Rimonabant; Thromboxanes; Vasoconstriction; Vasoconstrictor Agents

Previous studies indicate that in brain tissue the endocannabinoid 2-AG is inactivated by monoglyceride lipase (MGL)-catalyzed hydrolysis, and a recent report has indicated that MGL activity could be specifically inhibited by URB754 . In the present study, URB754 failed to inhibit 2-AG hydrolysis in rat brain preparations. In addition, brain cryosections were employed to assess whether URB754 could facilitate the detection of 2-AG-stimulated G protein activity. Nevertheless, whereas pretreatment with PMSF readily allowed detection of 2-AG-stimulated G protein activity, URB754 was ineffective. In contrast to previous claims, brain FAAH activity was also resistant to URB754. Thus, in our hands URB754 was not able to block the endocannabinoid-hydrolyzing enzymes and cannot serve as a lead structure for future development of MGL-specific inhibitors.

Topics: Aniline Compounds; Animals; Arachidonic Acids; Benzoxazines; Biphenyl Compounds; Brain; Catalysis; Endocannabinoids; Glycerides; GTP-Binding Proteins; Hydrolysis; Lectins; Lectins, C-Type; Male; Membrane Proteins; Molecular Structure; Rats; Rats, Wistar; Receptors, Cell Surface; Signal Transduction; Structure-Activity Relationship

The functions of 2-arachidonoylglycerol (2-AG), the most abundant endocannabinoid found in the brain, remain largely unknown. Here we show that two previously unknown inhibitors of monoacylglycerol lipase, a presynaptic enzyme that hydrolyzes 2-AG, increase 2-AG levels and enhance retrograde signaling from pyramidal neurons to GABAergic terminals in the hippocampus. These results establish a role for 2-AG in synaptic plasticity and point to monoacylglycerol lipase as a possible drug target.

Topics: Aniline Compounds; Animals; Arachidonic Acids; Benzoxazines; Cannabinoid Receptor Modulators; Dose-Response Relationship, Drug; Endocannabinoids; Enzyme Inhibitors; Glycerides; HeLa Cells; Hippocampus; Humans; Hydrolysis; In Vitro Techniques; Membrane Potentials; Monoacylglycerol Lipases; Neural Inhibition; Patch-Clamp Techniques; Pyramidal Cells; Rats; Signal Transduction