Faculty Collaboration Database

U-46619 but not serotonin increases endocannabinoid content in middle cerebral artery: evidence for functional relevance. Am J Physiol Heart Circ Physiol 2005 Jun;288(6):H2694-701

Date

02/08/2005

Pubmed ID

15695564

DOI

10.1152/ajpheart.00978.2004

Scopus ID

2-s2.0-19344367770 (requires institutional sign-in at Scopus site)   23 Citations

Abstract

Cerebral vascular smooth muscle cells express the CB(1) cannabinoid receptor, and CB(1) receptor agonists produce vasodilation of cerebral arteries. The purpose of this study was to determine whether vasoconstriction of rat middle cerebral artery (MCA) results in the local formation of endocannabinoids (eCBs), which, via activation of CB(1) receptors, oppose the vasoconstriction in a feedback manner. The thromboxane A(2) (TXA(2)) mimetic U-46619 significantly increased N-arachidonylethanolamine (AEA) and 2-arachidonylglycerol (2-AG) content of isolated MCA, whereas 5-hydroxytrypamine (5-HT) decreased AEA and 2-AG content. If eCBs play a feedback role in the regulation of MCA tone, then CB(1) receptor antagonists should enhance the constriction of MCA produced by U-46619 but not 5-HT. U-46619 caused concentration-dependent constrictions of endothelium-denuded MCA. Two CB(1) receptor antagonists SR-141716 and AM-251 decreased the EC(50) value for U-46619 to constrict endothelium-denuded MCA without affecting the maximal effect. A low concentration of CB(1) receptor agonist Win-55212-2 (30 nM) produced vasodilation of MCAs constricted with low but not saturating concentrations of U-46619. SR-141716 had no effect on the 5-HT concentration-contraction relationship. These data suggest that TXA(2) receptor activation increases MCA eCB content, which, via activation of CB(1) receptors, reduces the constriction produced by moderate concentrations of the TXA(2) agonist. Although 5-HT-induced vasoconstriction is reduced by exogenous CB(1) receptor agonist, activation of 5-HT receptors does not increase eCB content. These results suggest that MCA production of eCBs is not regulated by constriction per se but likely via a signaling pathway that is specific for TXA(2) receptors and not 5-HT receptors.

Author List

Rademacher DJ, Patel S, Ho WS, Savoie AM, Rusch NJ, Gauthier KM, Hillard CJ

Author

Cecilia J. Hillard PhD Associate Dean, Center Director, Professor in the Pharmacology and Toxicology department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid
Animals
Anterior Cerebral Artery
Cannabinoid Receptor Modulators
Diglycerides
Endocannabinoids
In Vitro Techniques
Male
Muscle, Smooth, Vascular
Phosphatidylethanolamines
Rats
Rats, Sprague-Dawley
Serotonin
Vasoconstrictor Agents