RT Journal Article SR Electronic T1 The Endogenous Cannabinoid Anandamide and Its Synthetic Analog R(+)-Methanandamide Are Intravenously Self-Administered by Squirrel Monkeys JF The Journal of Neuroscience JO J. Neurosci. FD Society for Neuroscience SP 5645 OP 5650 DO 10.1523/JNEUROSCI.0951-05.2005 VO 25 IS 23 A1 Justinova, Zuzana A1 Solinas, Marcello A1 Tanda, Gianluigi A1 Redhi, Godfrey H. A1 Goldberg, Steven R. YR 2005 UL http://www.jneurosci.org/content/25/23/5645.abstract AB Anandamide, an endogenous ligand for brain cannabinoid CB1 receptors, produces many behavioral effects similar to those of Δ9-tetrahydrocannabinol (THC), the main psychoactive ingredient in marijuana. Reinforcing effects of THC have been demonstrated in experimental animals, but there is only indirect evidence that endogenous cannabinoids such as anandamide participate in brain reward processes. We now show that anandamide serves as an effective reinforcer of drug-taking behavior when self-administered intravenously by squirrel monkeys. We also show that methanandamide, a synthetic long-lasting anandamide analog, similarly serves as a reinforcer of drug-taking behavior. Finally, we show that the reinforcing effects of both anandamide and methanandamide are blocked by pretreatment with the cannabinoid CB1 receptor antagonist rimonabant (SR141716). These findings strongly suggest that release of endogenous cannabinoids is involved in brain reward processes and that activation of cannabinoid CB1 receptors by anandamide could be part of the signaling of natural rewarding events.