CB2 receptor

CB2 (gene CNR2, chromosome 1p36) was cloned by Munro, Thomas, and Abu-Shaar (1993, Nature 365:61). Like CB1 it is Gi/o-coupled, but its distribution is predominantly peripheral immune — B cells, monocytes/macrophages, natural-killer cells, and mast cells — and central microglia, where expression rises sharply during neuroinflammation. This distribution underlies interest in CB2-selective agonists as non-intoxicating anti-inflammatory and analgesic agents, since activation does not produce the psychotropic effects associated with CB1. Multiple CB2-selective drug-discovery programs have advanced agonists and inverse agonists into clinical testing for pain, inflammatory bowel disease, and neurodegeneration; as of April 2026 no CB2-selective small molecule has reached approval. Endogenous ligands include 2-AG (full agonist) and anandamide (weak partial agonist); β-caryophyllene is a dietary CB2 agonist. → See also: CB1 receptor, Caryophyllene, 2-AG, Endocannabinoid system.