Inhibition of 2-arachidonoylglycerol catabolism modulates vasoconstriction of rat middle cerebral artery by the thromboxane mimetic, U-46619.
OBJECTIVE
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.


METHODS
The diameters of isolated, perfused MCA from male rats were measured using videomicroscopy.


RESULTS
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.


CONCLUSIONS
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.
Hillard
C J
CJ
Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, WI 53226, USA. chillard@mcw.edu
Ho
W-Sv
WS
Thompson
J
J
Gauthier
K M
KM
Wheelock
C E
CE
Huang
H
H
Hammock
B D
BD
D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid / Q000494:pharmacology*; D000581:Amidohydrolases / Q000037:antagonists & inhibitors; D000814:Aniline Compounds / Q000494:pharmacology; D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism / Q000494:pharmacology; D001095:Arachidonic Acids / Q000378:metabolism* / Q000494:pharmacology; D001549:Benzamides / Q000494:pharmacology; D048588:Benzoxazines / Q000494:pharmacology; D002219:Carbamates / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D063388:Endocannabinoids; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005989:Glycerides / Q000378:metabolism*; D066298:In Vitro Techniques; D008297:Male; D020768:Middle Cerebral Artery / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D009025:Morpholines / Q000494:pharmacology; D009281:Naphthalenes / Q000494:pharmacology; D009553:Nimodipine / Q000494:pharmacology; D010880:Piperidines / Q000494:pharmacology; D011720:Pyrazoles / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D043884:Receptor, Cannabinoid, CB1 / Q000037:antagonists & inhibitors; D000077285:Rimonabant; D013931:Thromboxanes / Q000494:pharmacology; D014661:Vasoconstriction / Q000187:drug effects*; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D000099252:Fatty Acid Amide Hydrolases
D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D000581:Amidohydrolases; D000814:Aniline Compounds; D016718:Arachidonic Acid; D001095:Arachidonic Acids; D001549:Benzamides; D048588:Benzoxazines; D002219:Carbamates; D063388:Endocannabinoids; D004791:Enzyme Inhibitors; D005989:Glycerides; D009025:Morpholines; D009281:Naphthalenes; D009553:Nimodipine; D010880:Piperidines; D011720:Pyrazoles; D043884:Receptor, Cannabinoid, CB1; D000077285:Rimonabant; D013931:Thromboxanes; D014662:Vasoconstrictor Agents; D000099252:Fatty Acid Amide Hydrolases; C462953:N-(2-methyl-3-hydroxyphenyl)-5,8,11,14-eicosatetraenamide; C514879:URB 754; C500528:cyclohexyl carbamic acid 3'-carbamoylbiphenyl-3-yl ester; 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