- published: 22 Feb 2016
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Tetrahydrocannabinol ( /ˌtɛtrəˌhaɪdrɵkəˈnæbɨnɒl/ tet-rə-HY-drə-kə-NAB-i-nol; THC), also known as delta-9-tetrahydrocannabinol (Δ9-THC), is the principal psychoactive constituent of the cannabis plant. First isolated in 1964, in its pure form, it is a glassy solid when cold, and becomes viscous and sticky if warmed. An aromatic terpenoid, THC has a very low solubility in water, but good solubility in most organic solvents, specifically lipids and alcohols.
Like most pharmacologically-active secondary metabolites of plants, THC in cannabis is assumed to be involved in self-defense, perhaps against herbivores but as of now it is still unknown. THC also possesses high UV-B (280-315 nm) absorption properties, which, it has been speculated, could protect the plant from harmful UV radiation exposure.
The pharmacological actions of THC result from its partial agonist activity at the cannabinoid receptor CB1, located mainly in the central nervous system, and the CB2 receptor, mainly expressed in cells of the immune system. The psychoactive effects of THC are primarily mediated by its activation of CB1G-protein coupled receptors, which result in a decrease in the concentration of the second messenger molecule cAMP through inhibition of adenylate cyclase.