Brain CB(2) Receptors: Implications for Neuropsychiatric Disorders

Although previously thought of as the peripheral cannabinoid receptor, it is now accepted that the CB(2) receptor is expressed in the central nervous system on microglia, astrocytes and subpopulations of neurons. Expression of the CB(2) receptor in the brain is significantly lower than that of the CB(1) receptor. Conflicting findings have been reported on the neurological effects of pharmacological agents targeting the CB(2) receptor under normal conditions. Under inflammatory conditions, CB(2) receptor expression in the brain is enhanced and CB(2) receptor agonists exhibit potent anti-inflammatory effects. These findings have prompted research into the CB(2) receptor as a possible target for the treatment of neuroinflammatory and neurodegenerative disorders. Neuroinflammatory alterations are also associated with neuropsychiatric disorders and polymorphisms in the CB(2) gene have been reported in depression, eating disorders and schizophrenia. This review will examine the evidence to date for a role of brain CB(2) receptors in neuropsychiatric disorders.