Fluorescent ligand binding reveals heterogeneous distribution of adrenoceptors and 'cannabinoid-like' receptors in small arteries

C. J. Daly, R. A. Ross, J. Whyte, C. M. Henstridge, A.J. Irving, J. C. McGrath

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Background and purpose: Pharmacological analysis of synergism or functional antagonism between different receptors commonly assumes that interacting receptors are located in the same cells. We have now investigated the distribution of alpha-adrenoceptors, beta-adrenoceptors and cannabinoid-like (GPR55) receptors in the mouse arteries.

Experimental approach: Fluorescence intensity from vascular tissue incubated with fluorescent ligands (alpha(1)-adrenoceptor ligand, BODIPY-FL-prazosin, QAPB; beta-adrenoceptor ligand, TMR-CGP12177; fluorescent angiotensin II; a novel diarylpyrazole cannabinoid ligand (Tocrifluor 1117, T1117) was measured with confocal microscopy. Small mesenteric and tail arteries of wild-type and alpha(1B/D)-adrenoceptor-KO mice were used.

Key results: T1117, a fluorescent form of the cannabinoid CB1 receptor antagonist AM251, was a ligand for GPR55, with low affinity for CB1 receptors. In mesenteric arterial smooth muscle cells, alpha(1A)-adrenoceptors were predominantly located in different cells from those with b-adrenoceptors, angiotensin receptors or cannabinoid-like (GPR55) receptors. Cells with beta-adrenoceptors predominated at arterial branches. Endothelial cells expressed beta-adrenoceptors, alpha-adrenoceptors and cannabinoid-like receptors. Only endothelial alpha-adrenoceptors appeared in clusters. Adventitia was a rich source of G protein-coupled receptors (GPCRs), particularly fibroblasts and nerve tracts, where Schwann cells bound alpha-adrenoceptor, beta-adrenoceptor and CB-receptor ligands, with a mix of separate receptor locations and co-localization.

Conclusions and implications: Within each cell type, each GPCR had a distinctive heterogeneous distribution with limited co-localization, providing a guide to the possibilities for functional synergism, and suggesting a new paradigm for synergism in which interactions may be either between cells or involve converging intracellular signalling processes. British Journal of Pharmacology (2010) 159, 787-796; doi:10.1111/j.1476-5381.2009.00608.x; published online 5 February 2010

Original languageEnglish
Pages (from-to)787-796
Number of pages10
JournalBritish Journal of Pharmacology
Issue number4
Publication statusPublished - Feb 2010


  • vascular smooth muscle
  • adrenoceptor
  • alpha(1B/D)-adrenoceptor knockout
  • fluorescent ligand binding
  • confocal microscopy
  • angiotensin
  • cannabinoid
  • adventitia
  • endothelium
  • GPR55

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