THC, short for tetrahydrocannabinol, is a chemical compound found in the cannabis plant, also known as marijuana. When used, either through ingestion or inhalation, it binds to specific receptors in the brain called cannabinoid receptors. In low doses, the compound causes some pain reduction, may reduce aggression, can stimulate appetite, and may help reduce nausea. Higher doses may cause the “high” associated with marijuana, leading to altered perception of time and space, and feelings of happiness or fatigue.
Pharmacology of THC
The pharmacological actions of THC result from its binding to the cannabinoid receptor CB1, located in the brain. The presence of these specialized receptors in the brain implied to researchers that endogenous cannabinoids are manufactured by the body, so the search began for a substance normally manufactured in the brain that binds to these receptors, the so-called natural ligand or agonist, leading to the eventual discovery of anandamide, 2-arachidonyl glyceride (2-AG), and other related compounds. This story resembles the discovery of the endogenous opiates (endorphins, enkephalins, and dynorphin), after the realization that morphine and other opiates bind to specific receptors in the brain.
In addition, it has been shown that cannabinoids, through an unknown mechanism, activate endogenous opioid pathways via the µ1 opioid receptor, precipitating a dopamine release in the nucleus accumbens. The effects of the drug can be suppressed by the CB1 cannabinoid receptor antagonist rimonabant (SR141716A) or, interesting to note, the opioid receptor antagonists (opioid blockers) naloxone and naloxonazine.