Treatment of Cannabinoid Withdrawal in Rhesus Monkeys

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Abstract Marijuana use is a public health concern. Withdrawal that occurs in over one-half of daily marijuana users is responsible, in part, for marijuana smoking. However, cannabinoids in marijuana produce a variety of therapeutic effects (analgesic and anti-emetic effects). While progress has been made toward establishing receptor mechanisms underlying the behavioral effects of cannabinoids, it is not clear whether the clinically useful actions and abuse liability of cannabinoids vary as a function of pharmacologic efficacy at cannabinoid receptors. Moreover, it is not clear whether pharmacologic modulation (e.g. decreased metabolism or cellular uptake) of endogenous cannabinoid agonists (e.g. anandamide) produces therapeutic effects and less of the non-preferred effects associated with direct cannabinoid agonism. This competing continuation of an R01 examines cannabinoid and non-cannabinoid approaches for treating marijuana withdrawal. This application further examines relationships between behavioral effects, pharmacologic (agonist) efficacy, and pharmacologic manipulation of endocannabinoid levels in assays predictive of marijuana-like effects in humans. Aim 1 uses a drug discrimination assay of rimonabant-induced cannabinoid withdrawal in rhesus monkeys to characterize the neuropharmacology of withdrawal that emerges upon discontinuation of treatment. Aim 2 explores relationships between pharmacologic (agonist) efficacy at cannabinoid receptors and behavioral effects. Tolerance and cross-tolerance among cannabinoids that vary in efficacy will be examined in rhesus monkeys discriminating ¿9-tetrahydrocannabinol (¿9-THC). This aim also establishes a discrimination assay with a high efficacy cannabinoid agonist and examines dependence to a high efficacy cannabinoid agonist, indexed by discriminative stimulus effects and overt signs of withdrawal. The ¿9-THC discrimination assay in rhesus monkeys was highly sensitive to exogenously administered anandamide, and this assay is used in Aim 3 to examine pharmacologic manipulation of endogenous cannabinoids and interactions between endocannabinoids and ¿9-THC. Aim 3 also examines modification of cannabinoid withdrawal by anandamide and inhibitors of its metabolism (URB 597) and uptake (AM 404). This competing continuation addresses a need for understanding the neuropharmacology of cannabinoids in behavioral assays predictive of marijuana-like intoxication and dependence. Collectively, studies in this competing continuation provide a framework for developing novel pharmacotherapies of marijuana withdrawal and cannabinoid-based therapeutics that could produce fewer adverse effects (i.e. abuse and dependence liability) than marijuana.