The importance of the endogenous cannabinoid system in various neuropsychiatric disorders

The endogenous cannabinoid system was first described in 1988. There are tw o specific receptors, the CB2-receptor, located in the lymphatic system (sp leen, lymphocytes), and the CB1-receptor occurring predominantly in the cen tral nervous system. The CB1-receptor shows a distinct distribution in the CNS with a very high density in the cerebellum, the basal ganglia and in th e hippocampus. In 1992 endogenous ligands of the cannabinoid system were di scovered for the first time (e.g. anandamide and 2-arachidonylglycerol). Th e physiological role of these arachidonic acid derivates is still unclear, Implications of these recent discoveries for the Gilles de la Tourette synd rome, ischaemic brain lesions, schizophrenic psychoses and opiate drug depe ndence are described, A dysregulation in the endogenous cannabinoid/anandam ide system could possibly play an import role in the etiology of Gilles de la Tourette syndrome and schizophrenic psychoses: administration of cannabi noids affects the symptoms of the Gilles de la Tourette syndrome positively , whereas cannabinoids probably have rather negative effects in schizophren ic psychoses, In ischaemic brain lesions cannabinoids seem to have a neurop rotective effect; they appear to minimize the extent of a lesion by reducti on of glutamate release. Additionally the meaning of the endogenous cannabi noid system for the development of opioid drug dependency is discussed and interactions between the endogenous opioid system and the endogenous cannab ainoid system are pointed out. This is of interest since it could be shown in animal experiments that the absence of CB1 receptors reduces the positiv e reinforcement of opiate administration.