Unlike terpenes, THC doesn't evaporate when it breaks down. It is completely transformed into another phytocannabinoid, called cannabinol (CBN). CBN is known for its relaxing properties. Compared to endogenous cannabinoids, the affinities and potencies of Δ9-THC for CB1 are comparable to those of AEA and 2AG.
However, the bioavailability of 9-THC varies depending on the depth of inhalation, duration of inhalation, and breath retention. The number of injections per session is also indicated during self-administration sessions in which Δ9-THC or cocaine was replaced with saline solution (sessions 4—). In addition, in populations with a low density of cannabinoid receptors, THC can even act as an antagonist of endogenous agonists that have greater efficacy on the receptors. The fact that THC is an illegal drug in most countries places restrictions on the supply and funding of research materials, as is the case in the United States, where the National Institute on Drug Abuse and the Drug Enforcement Administration continue to control the only federally legal source of cannabis for researchers.
However, clinical trials are needed to assess the importance of ATX inhibition by THC during medical cannabis use. Interestingly, it has been observed that only between 0.50% and 3.0% of the original amount of Δ9-THC in marijuana cigarettes contains 3.55% of Δ9-THC (approximately). The protection provided by Δ9-THC in diabetes is mediated by cannabinoid receptors and antioxidant properties. THC can stimulate CB2 receptors, which may slow the growth of some types of cancer and reduce arthritic pain and edema in models of arthritis.
As with other drugs of abuse, the acute reinforcing effects of Δ9-THC involve the activation of the mesocorticolimbic dopaminergic system. For this reason, several studies have focused THC and other cannabinoids on possible new drugs for the treatment of glaucoma, the main cause of irreversible blindness. The neuroprotective properties of THC may also be useful in this regard, as they have a dual effect on protecting the retina and the optic nerve. However, the FDA has approved dronabinol, a pharmaceutical form of THC, as an appetite stimulant for people with AIDS and as an antiemetic for people receiving chemotherapy under the trade names Marinol and Syndros.
Acute administration of Δ9-THC lowers the thresholds of intracranial self-stimulation in rats. THC, along with its double bond isomers and stereoisomers, is one of only three cannabinoids listed by the United Nations Convention on Psychotropic Substances (the other two are dimethylheptylpyran and parahexyl). In addition to apoptosis and the inhibition of proliferation, THC could exert its antitumor effects by inhibiting tumor angiogenesis and metastasis.