Cannabinoids, brain and behavior

Abstract

During the Last 15 years research has shown the existence of an endogenous system on the brain upon which the active ingredient of cannabis, Delta-9-tetrahydrocannabinol (Δ9-THC), exerts its actions. This system comprises cannabinoid receptors, endogenous ligands and enzymes for ligand biosynthesis and inactivation.  The main function of the endocannabinoid system is to regulate synaptic transmission in excitatory and inhibitory pathways in the brain. The CBI receptors are found predominantly in the brain with highest densities in the hippocampus, cerebellum, striatum and cortex. This localization justifies the effects of cannabinoids in the central nervous system Central effects of cannabi­noids include disnipton of psychomotor behaviour, short-term memory impair­ment, antinociceptive actions, stimulation of appetite and antiemetic effects. There are controversial data in the literature concerning the addictive potential of cannabis. Many animal studies have shown that tolerance develops to most of the behavioural and physiological effects of Δ9-THC. However, it is not clear that tolerance occurs to any significant extent in people who use infrequently modest amounts of marijuana. Although, classical drugs of abuse, that humans find pleasurable, can be shown to have positive reinforcing properties in animal behavioral models, it has been lather difficult to demonstrate the rewarding properties of Δ9-THC or synthetic cannabinoid agonists in preclinical studies, hi particular, many studies revealed that Δ 9-THC and cannabinoids have aversive properties. A significant withdrawal syndrome does not appear to occur in human cannabis users, although some symptoms comprising a psychological dependence have been reported in some users. Basic and clinical studies have shown that cannabis and cannabinoid agonists may have useful therapeutic implications. Medicines based on drugs that enhance the junction of endocannabinoids may offer in the future novel therapeutic opportunities with improved safety and efficacy.