Pharmacological targeting of nascent modulators of opioid signaling

PROJECT SUMMARY Opioids exert a plethora of behavioral effects that include clinically beneficial analgesia and untoward euphoria that leads to their abuse. Furthermore, prolonged exposure to opioids is associated with the development of dependence and tolerance that drive relapse and contribute to overdose and grave side- effects. All of these effects are mediated by the μ-opioid receptor (MOR), strategically positioned in neurons that form reward and nociceptive circuits. Furthermore, MOR signaling is involved in development of addiction to a wide range of drugs of abuse. The overarching goal of our efforts is to dissociate the behavioral effects associated with activation MOR signaling in neural circuits to curb the development of dependence. Our strategy to achieve this goal is to use large scale, unbiased approaches to identify novel modulators of MOR signaling and then apply high throughput chemical biology strategies to target these components with small molecule compounds. By conducting an unbiased forward genetic screen we have recently identified several novel receptor-like components that exert “anti-opioid” activity by modifying MOR signaling. Proof-of-principle experiments with knockout mice show that elimination of these elements profoundly alters behavioral responses to opioids diminishing the dependence and tolerance while increasing analgesia. Based on these observations we propose to use high throughput approach to develop pharmacological tools for redirecting MOR signals to specifically manipulate with opioid responses modifying addictive behaviors. Specifically, we plan to follow up on the discovery of the diverse set of compounds identified in high- throughput screening campaign, optimizing them using medicinal chemistry for achieving selective and specific alterations of MOR signaling. We will characterize the compounds and undertake their development efforts culminating in studying the effects on modifying opioid responses with circuit specific resolution using innovative optical strategies for recording neuromodulation in brain slices. Finally, we will investigate in vivo actions of the developed tool compounds testing their activity in rodent models of pain and addiction using a comprehensive battery of behavioral assays. These efforts will be paralleled by conducting in vivo pharmacokinetics, pharmacodynamics and toxicology studies. It is expected that this effort should result in a development of precision tools for understanding opioid receptor signaling and dissociating opioid effects with circuits and molecular specificity.