| Primary Identifier | IPR028335 | Type | Family |
| Short Name | GPR18 |
| description | Several 7TM receptors have been cloned but their endogenous ligands are unknown; these have been termed orphan receptors. However, recent research has identified certain pharmacological targets that could be investigated to find, for example, new potential cannabinoid receptors or channels [, , ]. GPR18 [, ], GPR55 [, ], GPR119 []show little structural similarity to CB1 and CB2 receptors, but they respond to endogenous agents analogous to the endogenous cannabinoid ligands, as well as some natural/synthetic cannabinoid receptor ligands []. However, because they do not fulfill all of the cannabinoid receptor criteria defined by IUPHAR, the classification of these proteins remains a contentious issue due to conflicting pharmacological results. As a result, they remain classified as putative endogenous agonists by IUPHAR [].This entry represents G protein-coupled receptor 18, also known as N-arachidonyl glycine receptor. It has been found to be a receptor for endogenous lipid neurotransmitters, several of which also bind to cannabinoid receptors [, , , ]. Recent research also supports the hypothesis that GPR18 is the abnormal cannabidiol receptor and N-arachidonoyl glycine, the endogenous lipid metabolite of anandamide, initiates directed microglial migration in the CNS through activation of GPR18 []. However, the pairing of GPR18 with N-arachidonoylglycine (NAGly) and tetrahydrocannabinol (THC) was not reproduced in two studies based on beta-arrestin assays [, ]. So, until further research allows a more definitive decision the function and nomenclature GPR18 is still being debated [, ]. |
