title: Antagonistic cannabinoid CB1/dopamine D2 receptor interactions in striatal CB1/D2 heteromers. A combined neurochemical and behavioral analysis.
abstract: In vitro results show the ability of the CB(1) receptor agonist CP 55,940 to reduce the affinity of D(2) receptor agonist binding sites in both the dorsal and ventral striatum including the nucleus accumbens shell. This antagonistic modulation of D(2) receptor agonist affinity was found to remain and even be enhanced after G-protein activation by Gpp(NH)p. Using the FRET technique in living HEK-293T cells, the formation of CB(1)-D(2) receptor heteromers, independent of receptor occupancy, was demonstrated. These data thereby indicate that the antagonistic intramembrane CB(1)/D(2) receptor-receptor interactions may occur in CB(1)/D(2) formed heteromers. Antagonistic CB(1)/D(2) interactions were also discovered at the behavioral level through an analysis of quinpirole-induced locomotor hyperactivity in rats. The CB(1) receptor agonist CP 55,940 at a dose that did not change basal locomotion was able to block quinpirole-induced increases in locomotor activity. In addition, not only the CB(1) receptor antagonist rimonobant but also the specific A(2A) receptor antagonist MSX-3 blocked the inhibitory effect of CB(1) receptor agonist on D(2)-like receptor agonist-induced hyperlocomotion. Taken together, these results give evidence for the existence of antagonistic CB(1)/D(2) receptor-receptor interactions within CB(1)/D(2) heteromers in which A(2A) receptors may also participate.
authors.affiliation: Department of Neuroscience, Karolinska Institutet, Retzius väg 8, 17177 Stockholm, Sweden.
authors.forename: Daniel
authors.initials: D
authors.lastname: Marcellino
authors.forename: Paulina
authors.initials: P
authors.lastname: Carriba
authors.forename: Malgorzata
authors.initials: M
authors.lastname: Filip
authors.forename: Anders
authors.initials: A
authors.lastname: Borgkvist
authors.forename: Malgorzata
authors.initials: M
authors.lastname: Frankowska
authors.forename: Inmaculada
authors.initials: I
authors.lastname: Bellido
authors.forename: Sergio
authors.initials: S
authors.lastname: Tanganelli
authors.forename: Christa E
authors.initials: CE
authors.lastname: Müller
authors.forename: Gilberto
authors.initials: G
authors.lastname: Fisone
authors.forename: Carme
authors.initials: C
authors.lastname: Lluis
authors.forename: Luigi F
authors.initials: LF
authors.lastname: Agnati
authors.forename: Rafael
authors.initials: R
authors.lastname: Franco
authors.forename: Kjell
authors.initials: K
authors.lastname: Fuxe
mesh_terms: D000818:Animals; D001522:Behavior, Animal; D002461:Cell Line, Transformed; D003342:Corpus Striatum / Q000187:drug effects / Q000378:metabolism*; D003511:Cyclohexanols / Q000494:pharmacology; D004298:Dopamine / Q000494:pharmacology; D018491:Dopamine Agonists; D065127:Dopamine D2 Receptor Antagonists; D004347:Drug Interactions; D031541:Fluorescence Resonance Energy Transfer / Q000379:methods; D006165:Guanylyl Imidodiphosphate / Q000494:pharmacology; D006801:Humans; D008164:Luminescent Proteins / Q000378:metabolism; D008297:Male; D009043:Motor Activity / Q000502:physiology*; D011485:Protein Binding / Q000187:drug effects; D019257:Quinpirole / Q000494:pharmacology; D011859:Radiography; D051381:Rats; D017207:Rats, Sprague-Dawley; D017208:Rats, Wistar; D043884:Receptor, Cannabinoid, CB1 / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D043882:Receptors, Cannabinoid / Q000378:metabolism; D017448:Receptors, Dopamine D2 / Q000378:metabolism*; D014162:Transfection / Q000379:methods
chemical_list: D003511:Cyclohexanols; D018491:Dopamine Agonists; D065127:Dopamine D2 Receptor Antagonists; D008164:Luminescent Proteins; D043884:Receptor, Cannabinoid, CB1; D043882:Receptors, Cannabinoid; D017448:Receptors, Dopamine D2; D019257:Quinpirole; D006165:Guanylyl Imidodiphosphate; C054649:3-(2-hydroxy-4-(1,1-dimethylheptyl)phenyl)-4-(3-hydroxypropyl)cyclohexanol; D004298:Dopamine