The endocannabinoid system: emotion, learning and addiction.
The identification of the cannabinoid receptor type 1 (CB1 receptor) was the milestone discovery in the elucidation of the behavioural and emotional responses induced by the Cannabis sativa constituent Delta(9)-tetrahydrocannabinol. The subsequent years have established the existence of the endocannabinoid system. The early view relating this system to emotional responses is reflected by the fact that N-arachidonoyl ethanolamine, the pioneer endocannabinoid, was named anandamide after the Sanskrit word 'ananda', meaning 'bliss'. However, the emotional responses to cannabinoids are not always pleasant and delightful. Rather, anxiety and panic may also occur after activation of CB1 receptors. The present review discusses three properties of the endocannabinoid system as an attempt to understand these diverse effects. First, this system typically functions 'on-demand', depending on environmental stimuli and on the emotional state of the organism. Second, it has a wide neuro-anatomical distribution, modulating brain regions with different functions in responses to aversive stimuli. Third, endocannabinoids regulate the release of other neurotransmitters that may have even opposing functions, such as GABA and glutamate. Further understanding of the temporal, spatial and functional characteristics of this system is necessary to clarify its role in emotional responses and will promote advances in its therapeutic exploitation.
Moreira
Fabrício A
FA
Department of Physiological Chemistry, Johannes Gutenberg University Mainz, Duesbergweg 6, 55099 Mainz, Germany. moreira@uni-mainz.de
Lutz
Beat
B
D000818:Animals; D001007:Anxiety / Q000139:chemically induced / Q000503:physiopathology; D001143:Arousal / Q000187:drug effects / Q000502:physiology; D001921:Brain / Q000187:drug effects / Q000503:physiopathology*; D063385:Cannabinoid Receptor Modulators / Q000502:physiology*; D002186:Cannabinoids / Q000494:pharmacology* / Q000627:therapeutic use / Q000633:toxicity; D003863:Depression / Q000139:chemically induced / Q000503:physiopathology; D004305:Dose-Response Relationship, Drug; D013759:Dronabinol / Q000494:pharmacology; D004644:Emotions / Q000187:drug effects* / Q000502:physiology*; D063388:Endocannabinoids; D005239:Fear / Q000187:drug effects / Q000502:physiology; D006801:Humans; D007858:Learning / Q000187:drug effects* / Q000502:physiology*; D002189:Marijuana Abuse / Q000503:physiopathology* / Q000523:psychology; D051379:Mice; D018377:Neurotransmitter Agents / Q000378:metabolism; D043884:Receptor, Cannabinoid, CB1 / Q000187:drug effects* / Q000502:physiology*; D013375:Substance Withdrawal Syndrome / Q000503:physiopathology / Q000523:psychology; D019966:Substance-Related Disorders / Q000503:physiopathology* / Q000523:psychology
D063385:Cannabinoid Receptor Modulators; D002186:Cannabinoids; D063388:Endocannabinoids; D018377:Neurotransmitter Agents; D043884:Receptor, Cannabinoid, CB1; D013759:Dronabinol