EtOH Seeking and Relapse: Therapeutic Potential of Transdermal Cannabidiol

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A major challenge for the successful treatment of alcoholism is long-lasting susceptibility to relapse. Several processes have been implicated in the compulsion to resume drinking during abstinence. These include drinking urges produced by ethanol (EtOH)-related environmental cues or contexts, EtOH-induced neuroadaptation resulting in anxiety and hypersensitivity to stress, as well as cognitive deficits associated with EtOH-induced neurodegeneration that can lead to impaired impulse control. Thus, considering that various risk factors exist that elicit vulnerability states in alcoholics, approaches to treatment drug discovery aimed at providing protection for multiple precipitating factors are likely to be more effective than approaches targeting only a single factor. An agent with an emerging profile of actions relevant for multiple relapse vulnerability states is cannabidiol (CBD), the main non-psychoactive and non-addictive component of the cannabis sativa plant. A factor limiting CBD's therapeutic potential in man has been the drug's low oral bioavailability paired with lack of a readily available and suitable drug delivery method. However, evidence has become available that the transdermal route of administration provides an effective delivery method for CBD. Therefore, preclinical evaluation of the profile of actions of transdermal CBD (tCBD) is timely and will close a major gap in knowledge on CBD's clinical potential. Preliminary studies confirmed that tCBD ameliorates several vulnerability states associated with relapse risk as measured by attenuation of cue- and stress-induced reinstatement of EtOH seeking, anxiety-like behavior, and reversal of impulsive behavior following EtOH intoxication. Of particular significance was the finding that the reduction of EtOH seeking remained unabated at the end of a nearly five-month post-treatment test period. This observation, paired with the attenuation of EtOH-induced impulsivity, is of substantial interest from both a medication development and neurobiological perspective in that it is suggestive of neuroregulatory actions of CBD that restore normal function to circuitries regulating reward, incentive motivation, impulsivity, stress and anxiety. The purpose of this project is to confirm the hypothesis that tCBD has therapeutic potential for multiple vulnerability states associated with relapse risk. This will be accomplished using rats with a history of EtOH dependence, a status essential for providing translational relevance, as follows: By establishing the short- and long-term profile of tCBD actions (1) on compulsive EtOH seeking and relapse, (2) on post-withdrawal manifestations of negative affect as measured by anxiety-like behavior and sensitivity to stress challenges, and (3) on impaired impulse control produced by EtOH intoxication. A parallel objective is to identify neuropharmacological systems mediating the diverse behavioral effects of tCBD and to examine whether tCBD has neuroprotective or proneurogenic actions relevant for the prevention or reversal of impaired impulse control. The results are likely to have significant implications for treatment drug development and understanding of the neural basis of relapse.