Short answer: No. A 2010 cell study found evidence that the endogenous lipid N-arachidonoyl glycine, or NAGly, drove microglial migration through GPR18—a receptor outside the familiar CB1 and CB2 framework. The work also connected GPR18 to the previously unidentified “abnormal cannabidiol” receptor.
Microglia are immune-surveillance cells in the central nervous system. After injury or infection, they can change phenotype and migrate toward affected tissue. The chemical signal matters because different attractants may be associated with protective, reparative, or pro-inflammatory responses.
Prior pharmacology suggested that microglial migration could be regulated by CB2 and by another G-protein-coupled receptor activated by abnormal cannabidiol, a synthetic CBD isomer that does not act like a conventional CB1 or CB2 agonist. The molecular identity of that receptor was uncertain.
The researchers used BV-2 microglial cells and human embryonic kidney cells engineered to express GPR18 or GPR55. They evaluated migration, cell proliferation, MAP kinase activation, receptor expression, and responses to agonists and antagonists.
NAGly produced directed migration at sub-nanomolar concentrations in BV-2 cells and GPR18-transfected cells. It did not produce the same effect in GPR55-transfected or unmodified kidney cells. Abnormal cannabidiol produced a similar pattern. The migration was blocked or attenuated by compounds associated with abnormal-cannabidiol receptor pharmacology, while the cells showed GPR18 messenger RNA and immunostaining.
“Cannabinoid effect” is not synonymous with “CB1 effect.” Endogenous lipids, plant cannabinoids, metabolites, and synthetic analogues can engage different targets with different efficacies. A compound may also behave as a partial agonist in one expression system and an antagonist-like compound in another.
That complexity matters when a mechanistic claim is used to explain impairment, toxicity, or therapeutic action. Naming a receptor is only one step. The evidence must also address concentration, target engagement, cell type, downstream signaling, and whether the mechanism operates in the intact organism at the exposure in question.
This was a cellular migration study, not a human exposure or impairment study. BV-2 cells are an experimental model, and engineered receptor-expression systems can differ from normal tissue. The study supported GPR18 as the putative abnormal-cannabidiol receptor and identified a potent NAGly response, but it did not establish a clinical treatment or a direct behavioral effect.
Source: McHugh D et al. PubMed record (PMID 20346144); full article DOI.