THC is the main psychoactive component of cannabis. In this video, I discuss the effects of THC on the nervous system.
THC is the main psychoactive component of cannabis, and one of a class of compounds known as cannabinoids. Cannabis tends to be relatively low in THC compared to its levels of a THC precursor, THCA. Heating the cannabis plant, however, causes the conversion of THCA to THC, which is part of the basis for heating or burning the plant for use. The effects of cannabis may vary depending on the variety of cannabis plant and its associated levels of THC and other cannabinoids, but common effects of THC include: euphoria, sedation, stimulation of appetite, impaired cognitive function, analgesia, and anxiety.
THC is thought to exert most of its effects by binding to receptors called cannabinoid receptors. There are two known cannabinoid receptors, CB1 and CB2–both of which are g-protein coupled receptors. CB1 receptors are found throughout the nervous system, while CB2 receptors are primarily found on immune cells. THC acts as a partial agonist at cannabinoid receptors, meaning it binds to these receptors and generates a response that’s a fraction of what other substances that bind to the receptors can generate. THC interacts with a number of other targets as well, but it’s thought that its main psychoactive effects are mediated through its action at CB1 receptors.
Activation of CB1 receptors is thought to lead to the modulation of the release of various neurotransmitters. It’s not fully understood how this translates into the characteristic effects of THC, but the activation of CB1 receptors in different areas of the nervous system may partially explain the effects of the drug. CB1 receptors in areas like the cortex and hippocampus, for example, may be involved in the perceptual and cognitive effects of THC, CB1 receptors in areas like the basal ganglia and cerebellum may be associated with sedation and effects on movement, and CB1 receptors in areas like the spinal cord and brainstem may be linked to analgesic effects.
Banister SD, Arnold JC, Connor M, Glass M, McGregor IS. Dark Classics in Chemical Neuroscience: Δ9-Tetrahydrocannabinol. ACS Chem Neurosci. 2019;10(5):2160‐2175. doi:10.1021/acschemneuro.8b00651
Howlett AC, Barth F, Bonner TI, et al. International Union of Pharmacology. XXVII. Classification of cannabinoid receptors. Pharmacol Rev. 2002;54(2):161‐202. doi:10.1124/pr.54.2.161
Pertwee RG. Pharmacological actions of cannabinoids. Handb Exp Pharmacol. 2005;(168):1‐51. doi:10.1007/3-540-26573-2_1
Pertwee RG. The diverse CB1 and CB2 receptor pharmacology of three plant cannabinoids: delta9-tetrahydrocannabinol, cannabidiol and delta9-tetrahydrocannabivarin. Br J Pharmacol. 2008;153(2):199‐215. doi:10.1038/sj.bjp.0707442