Central Effect of Components of Cannabis: Utility and Risk

Abstract

Cannabis contains over 700 known cannabinoids, terpenoids, flavonoids, and so on; however, the roles and importance of these components have yet to be fully understood. Δ9-Tetrahydrocannabinol (THC) is believed the most psychoactive component in cannabis, whereas cannabidiol (CBD), cannabinol, and cannabigerol are the most well-known non-psychoactive components. THC, but not CBD, has been shown to produce abnormal behavior in animals; these effects are caused, at least in part, by binding to cannabinoid receptor type 1 (CB1) in the brain. Regarding the risks associated with cannabis use, acute effects of THC, such as a "high", cognitive deficits, and irritability, are considered more important than potential dependence. On the other hand, CBD has shown anticonvulsant, anti-inflammatory, immunosuppressive, analgesic, and anticancer effects. However, CBD has very low affinity (in the micromolar range) for the CB1 receptor, as well as for the CB2 receptor, and its underlying mechanism remains obscure. In this review, we demonstrate that THC induces abnormal behavior such as catalepsy-like immobilization, spatial memory impairment, and high and low sensitivity to ultrasonic vocalization after an aversive air-puff stimulus. Moreover, we demonstrate that THC and CBD improve brain injury in middle cerebral artery occlusion in a mouse model through different mechanisms. These findings suggest the need to discuss the recent development of "THC and CBD pharmacology" in animal studies, as well as the utility and risk of various cannabis components in humans.