Until 1993, the endocannabidnoid system was unknown. Researchers stumbled over the discovery when a CB1 receptor was activated. Further investigation of neurotransmission related to the CB1 receptor led to the discovery of Anandamide, a naturally occurring cannabinoid. The Endocannabidnoid system consists of CB1 and CB2 receptors, the ligands that bind to them, like Anandamide or CBD, and the tissues where reception takes place. Cannabinoids that are indigenous to the body are known as endocannabidnoids. This would include neurotransmitters such as Anandamide (AEA), and 2-AG. Exocannabidnoids are derived from external sources, examples would include, Cannabidiol (CBD), Tetrahydrocannabinol (THC), and Sativex. While both CB receptors are present in small quantities throughout the body, the primary concentration of CB1 receptors is found in the Central Nervous System (CNS). CB2 receptors are primarily concentrated throughout the immune system. CBD also activates other receptors that are not solely defined as ECS receptors, such as TRPV1, also known as the “Vannillanoid receptor”, and 5-HT1A, a serotonin receptor 2018.

Concentration locations of CB1 and CB2 receptors

The above figure shows an example of CB2 receptors located on T-cells, a specialized immunity cell. CB1 receptors are located on the cell membrane of neurons in the brain. This figure does not represent every type of cell with CB receptors, but is a simplified example of their locations.