O-1918 is a synthetic compound related to cannabidiol, which is an antagonist at two former orphan receptorsGPR18 and GPR55, that appear to be related to the cannabinoid receptors. O-1918 is used in the study of these receptors, which have been found to be targets for a number of endogenous and synthetic cannabinoid compounds, and are thought to be responsible for most of the non-CB1, non-CB2 mediated effects that have become evident in the course of cannabinoid research.
^Offertáler, L.; Mo, F. M.; Bátkai, S.; Liu, J.; Begg, M.; Razdan, R. K.; Martin, B. R.; Bukoski, R. D.; Kunos, G. (2003). "Selective ligands and cellular effectors of a G protein-coupled endothelial cannabinoid receptor". Molecular Pharmacology. 63 (3): 699–705. doi:10.1124/mol.63.3.699. PMID12606780.
^Schuelert, N.; McDougall, J. J. (2011). "The abnormal cannabidiol analogue O-1602 reduces nociception in a rat model of acute arthritis via the putative cannabinoid receptor GPR55". Neuroscience Letters. 500 (1): 72–76. doi:10.1016/j.neulet.2011.06.004. PMID21683763.
^Szczesniak, A. M.; Maor, Y.; Robertson, H.; Hung, O.; Kelly, M. E. M. (2011). "Nonpsychotropic Cannabinoids, Abnormal Cannabidiol and Canabigerol-Dimethyl Heptyl, Act at Novel Cannabinoid Receptors to Reduce Intraocular Pressure". Journal of Ocular Pharmacology and Therapeutics. 27 (5): 427–435. doi:10.1089/jop.2011.0041. PMID21770780.