Endocannabinoids & Mechanisms of action

Until quite recently it was unknown how cannabis caused its effects on the brain. Initially it was assumed that cannabinoids such as THC simply dissolve in cell membranes in the brain, thereby disrupting the function of brain cells, similar to the way alcohol makes you feel drunk. Then something revolutionary happened; in the 1990’s the human endocannabinoid system was discovered, and we learned that many of our own bodily functions are controlled by cannabis-like substances produced in the brain, immune system and other organs. 

Endocannabinoids

Receptors: how cells communicate 

 A receptor is a large molecule found on the surface of a cell. Here it receives chemical or physical signals from outside the cell. This is the most important way for a cell to respond to changes in its environment. Hundreds of different receptor types are found on an average cell. Each receptor type binds only certain substances. A substance that binds to a receptor is called a ligand. In general, ligands are small molecules such as a neurotransmitter (e.g. dopamine), hormone (testosterone), pharmaceutical drug (beta-blockers), toxin (from a virus or bacteria), or… a cannabinoid like THC. 

When a ligand binds to its corresponding receptor it changes the receptor’s setting, quite similar to how a lock requires a specific key to open it. When this happens, the received signal urges the cell to do ‘something’ that is specifically linked with that receptor, such as grow (e.g. to heal a wound), die (e.g. make place for new cells), produce chemicals (e.g. to digest food, to fight infection), or allow specific substances to enter the cell (e.g. building materials for the cell). Because the biological effect of many (pharmaceutical) drugs takes place through interaction with receptors, it makes sense that the psychoactive effects observed for THC led to the scientific hunt for specific cannabinoid receptors. 

This finally resulted in the identification of Cannabinoid-Binding receptor type 1 (CB-1, 1990), soon followed by discovery of a type 2 receptor (CB-2, 1993). Currently, there is even speculation about a possible CB-3 receptor, but this has not yet been fully confirmed.
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