The endocannabinoid system includes 2 types of G-protein coupled receptors: CB1 (mostly in the brain) and CB2 (in peripheral lymphoid tissue). The major cannabinoid ligands are arachidonylethanolamine ("anandamide," the Sanskrit word for bliss) and 2-arachidonylglycerol ("2AG"). It is by binding to CB1 receptors that δ-9-tetrahydrocannabinol (THC), the principal psychoactive ingredient in marijuana ("pot"), produces its intended subjective effects.