Addiction and Pain: Cannabinoid and Opioid Interactions The goal of this special issue of Current Drug Targets is to report and update our current knowledge in molecular and functional aspects of cannabinoid and opioid interactions in relation to addiction and pain. It has been known for several years that cannabinoids and opioids share several pharmacological actions such as antinociception, sedation, hypothermia and hypotension. However, only recent evidence has suggested that these two systems interact and are involved in many physiological and pathological functions. This cross talk could be a target for intervention in the treatment of pain and addiction. In the current issue several leading investigators report new findings about molecular mechanisms behind this interaction. Additionally, the role of cannabinoid-opioid relationship is reviewed in relationship to pain and drugs of abuse such as nicotine, MDMA and alcohol. Dr. Parolaro and co-workers review focuses on molecular mechanisms underlying central and peripheral interactions. The authors highlight the relevance of receptor co-expression and signal transduction mechanisms. They also suggest that the nature of opioid and cannabinoid interaction could differ between circuits mediating addiction and those mediating other functions such as antinociception, emotion and cognition. The addiction aspect of this issue commences with Dr. Lopez-Moreno and co-workers review of the role of functional interactions between the opioid and endocannabinoid systems in alcohol relapse behavior. They also discuss the link between receptor polymorphism that lead to altered opioid and cannabinoid neurotransmission leading to an increased propensity to drug addiction. MDMA (ecstasy) is an addictive amphetamine derivative with psychostimulant properties. The role of the opioid and endocannabinoid system as a modulator of the rewarding/reinforcing properties of MDMA is reviewed by Dr. Robledo. Dr. Maldonado and Dr. Berrendero review recent behavioural and biochemical data on the role of cannabinoid and opioid neurotransmission in the different processes linked to nicotine addiction. They conclude their review by suggesting pharmacological manipulations as a potential therapeutical strategy for treating nicotine and perhaps addiction to other drugs of abuse. Based on the knowledge that that maternal exposure to drugs alters brain circuits, Dr. Spano and co-workers examined molecular and behavioural consequences of maternal exposure to opioids and cannabinoids. They also reviewed the impact of long term exposure at different developmental stages concluding that at least in pre-clinical studies exposure to both cannabinoids and opioids at early developmental stages predicts greater likelihood of intake in adulthood. The issue finalises with Dr. Desroches and Dr. Beaulieu review which focuses on cannabinoid and opioid interactions in pain modulation. They highlight potential of additive or even synergistic antinociceptive effects of both neurotransmitter systems, emphasising their clinical relevance. I would like to thank all the contributors of this special issue for their time, experience, and insights to these important topics.
Current Drug Targets aims to cover the latest and most outstanding developments on the medicinal chemistry and pharmacology of molecular drug targets e.g. disease specific proteins, receptors, enzymes, genes. Each issue of the journal will be devoted to a single timely topic, with series of in-depth reviews, written by leaders in the field, covering a range of current topics on drug targets. These issues will be organized and led by a guest editor who is a recognized expert in the overall topic. As the discovery, identification, characterisation and validation of novel human drug targets for drug discovery continues to grow; this journal will be essential reading for all pharmaceutical scientists involved in drug discovery and development.