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Identification of N ‐arachidonoyl dopamine as a highly biased ligand at cannabinoid CB 1 receptors
Author(s) -
Redmond William J.,
Cawston Erin E.,
Grimsey Natasha L.,
Stuart Jordyn,
Edington Amelia R.,
Glass Michelle,
Connor Mark
Publication year - 2016
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/bph.13341
Subject(s) - cannabinoid receptor , cannabinoid , cannabinoid receptor agonists , cannabinoid receptor type 2 , agonist , receptor , gpr18 , endocannabinoid system , g protein coupled receptor , chemistry , adenylyl cyclase , pharmacology , cannabinoid receptor antagonist , microbiology and biotechnology , biology , biochemistry
Background and Purpose N ‐arachidonyl dopamine (NADA) has been identified as a putative endocannabinoid, but there is little information about which signalling pathways it activates. The purpose of this study was to identify the signalling pathways activated by NADA in vitro . Experimental Approach Human or rat cannabinoid CB 1 receptors were expressed in AtT20, CHO or HEK 293 cells. NADA displacement of radiolabelled cannabinoids, and CB 1 receptor mediated activation of K channels or ERK phosphorylation, release of intracellular calcium ([Ca] i ) and modulation of adenylyl cyclase were measured in addition to NADA effects on CB 1 receptor trafficking. Key Results At concentrations up to 30 μM, NADA failed to activate any signalling pathways via CB 1 receptors, with the exception of mobilization of [Ca] i . The elevations of [Ca] i were insensitive to pertussis toxin, and reduced or abolished by blockers of G q / 11 ‐dependent processes including U73122, thapsigargin and a peptide antagonist of G q / 11 activation. Prolonged NADA incubation produced modest loss of cell surface CB 1 receptors. The prototypical cannabinoid agonist CP55940 signalled as expected in all assays. Conclusions and Implications NADA is an ineffective agonist at most canonical cannabinoid receptor signalling pathways, but did promote mobilization of [Ca] i via G q ‐dependent processes and some CB 1 receptor trafficking. This signalling profile is distinct from that of any known cannabinoid, and suggests that NADA may have a unique spectrum of effects in vivo . Our results also indicate that it may be possible to identify highly biased CB 1 receptor ligands displaying a subset of the pharmacological or therapeutic effects usually attributed to CB 1 ligands.