TY - JOUR T1 - Evidence for a New G Protein-Coupled Cannabinoid Receptor in Mouse Brain JF - Molecular Pharmacology JO - Mol Pharmacol SP - 155 LP - 163 DO - 10.1124/mol.60.1.155 VL - 60 IS - 1 AU - Christopher S. Breivogel AU - Graeme Griffin AU - Vincenzo Di Marzo AU - Billy R. Martin Y1 - 2001/07/01 UR - http://molpharm.aspetjournals.org/content/60/1/155.abstract N2 - The purpose of these studies was to support the hypothesis that an undiscovered cannabinoid receptor exists in brain. [35S]GTPγS binding was stimulated by anandamide and WIN55212-2 in brain membranes from both CB1 +/+and CB1 −/− mice. In contrast, a wide variety of other compounds that are known to activate CB1receptors, including CP55940, HU-210, and Δ9-tetrahydrocannabinol, failed to stimulate [35S]GTPγS binding in CB1 −/−membranes. In CB1 −/− membranes, SR141716A affected both basal and anandamide- or WIN55212-2-induced stimulation of [35S]GTPγS binding only at concentrations greater than 1 μM. In CB1 +/+ membranes, SR141716A inhibited only 84% of anandamide and 67% of WIN55212-2 stimulated [35S]GTPγS binding with an affinity appropriate for mediation by CB1 receptors (K B ≈ 0.5 nM). The remaining stimulation seemed to be inhibited with lower potency (IC50 ≈ 5 μM) similar to that seen in CB1 −/− membranes or in the absence of agonist. Further experiments determined that the effects of anandamide and WIN55212-2 were not additive, but that the effect of μ opioid, adenosine A1, and cannabinoid ligands were additive. Finally, assays of different central nervous system (CNS) regions demonstrated significant activity of cannabinoids in CB1 −/− membranes from brain stem, cortex, hippocampus, diencephalon, midbrain, and spinal cord, but not basal ganglia or cerebellum. Moreover, some of these same CNS regions also showed significant binding of [3H]WIN55212-2, but not [3H]CP55940. Thus anandamide and WIN55212-2 seemed to be active in CB1 −/− mouse brain membranes via a common G protein-coupled receptor with a distinct CNS distribution, implying the existence of an unknown cannabinoid receptor subtype in brain. THCtetrahydrocannabinolGTPγSguanosine-5′-O-(3-thiotriphosphate)CNScentral nervous systemDAMGO[d-Ala2,N-Me-Phe4,Gly5-ol]-enkephalinPIAN6-(2-phenylisopropyl)adenosineBSAbovine serum albuminANOVAanalysis of variance ER -