CNR1 gene encodes a protein that is one of two cannabinoid receptors. The cannabinoids, principally delta-9-tetrahydrocannabinol and synthetic analogs, are psychoactive ingredients of marijuana. The cannabinoid receptors are members of the family of guanine-nucleotide-binding protein (G-protein) coupled receptors which inhibit adenylate cyclase activity in a dosedependent, stereoselective and pertussis toxinsensitive manner. The two receptors have been found to be involved in the cannabinoidinduced CNS effects (including alterations in mood and cognition) experienced by users of marijuana. Two transcript variants encoding different isoforms have been described for this gene.