Cannabinoid receptors and their relationships with neuropsychiatric disorders.

Cannabinoids are the costituents of the marijuana plants. The central effects of exogenous cannabinoids
are implicated in enhancing mood, altering emotional states, and interfering in the formation of short-term
memory. Cannabinoid receptors are G protein-coupled receptors with seven transmembrane domains that
are expressed on the cell surface with their binding domain exposed to the extracellular space. To date, two
cannabinoid receptors have been cloned, CB1 and CB2. Recent evidence suggests that a third ‘CB3’
receptor is out there, waiting to be cloned. The endocannabinoids may represent the first members of a new
classes of neuromodulators, that are not stored in cell vesicles, but rather synthesised by the cell on demand.
The endogenous cannabinoid system could play a central role in several neuropsychiatric disorders and is
also involved in other conditions such as pain, spasticity and neuroprotection. Implication of cannabinoid
system in the pathogenesis and development of schizophrenia is also discussed.