The GPR18 gene (G Protein-Coupled Receptor 18 gene) is a protein-coding gene located on chromosome 13q32.3. G protein-coupled receptors (GPCRs) form the largest receptor family, transduce environmental stimuli into changes in cell behavior, and are important drug targets. Many GPCRs, including GRP18, are classified as orphan receptors due to limited knowledge about their ligands and their coupling to cellular signaling mechanisms (Morri M et al. 2018)
GPR18 encodes a receptor protein, the endocannabinoid N-arachidonylglycine (NAGly ). This receptor can also be activated by herbal and synthetic cannabinoid agonists e.g. 9 -tetrahydrocannabinol (THC=dronabinol) (Miller S et al. 2018). For example, THC lowers intraocular pressure by activating GPR18 (and CB1).