Cannabinoid receptors are of a class of cell membrane receptors under the G protein-coupled receptor superfamily. As is typical of G protein-coupled receptors, the cannabinoid receptors contain seven transmembrane spanning domains.

The G protein-coupled receptor (GPCR) family is the largest family of membrane proteins in eukaryotes. It encodes at least 800 human genes. But endogenous ligands of more than 140 GPCRs have not been determined. Such GPCRs are referred to as orphan G