It is well known that the brain and body contain receptors that bind to tetrahydro-cannabinol (THC) the active ingredient in marijuana and that the body naturally produces substances known as cannabinoids that bind to these receptors. There are two known cannabinoid receptors, CB1 is located on neurons in the brain and spinal cord, and CB2 is located primarily on immune cells. Prior to the present study, it was unknown whether CB2 receptors could be found on neurons in the brain and what role they might play in brain function.
In this study, researchers found that CB2 receptors and their genes are located in neurons that contain dopamine in the ventral tegmental area, a brain area that is involved in reward and drug addiction. Activation of these receptors caused a reduction in cocaine self-administration by mice, suggesting a role for these receptors in modulating reward from cocaine. These findings suggest a new target for both understanding how cocaine acts in the brain and for developing effective treatments for cocaine addiction. They also provide insight into the role of the brain’s natural receptors for chemicals found in marijuana and suggest the need for additional research to understand the role these receptors play in normal brain functioning and abuse of drugs.
Cannabinoid CB2 receptors modulate midbrain dopamine neuronal activity and dopamine-related behavior in mice. Zhang HY, Gao M, Liu QR, Bi GH, Li X, Yang HJ, Gardner EL, Wu J, Xi ZX. Proc Natl Acad Sci U S A. 2014 Nov 3. doi:pii: 201413210. http://www.ncbi.nlm.nih.gov/pubmed/25368177