RESEARCH & RELATED - OTHER PROJECT INFORMATION - PROJECT SUMMARY/ABSTRACT In this Program Project renewal application, we propose to fundamentally expand current understanding of the variable potentially functional modulations of the CB1 and CB2 cannabinoid receptors. During this current period, our work has resulted in the development of a number of key pharmacologically diverse and selective agonists and antagonists for CB1 and CB2 cannabinoid receptors. We also produced detailed information on the structures of these two receptors. Based upon the strengths of this foundational work, we now propose to develop new functionally selective tools for fine tuning CB1 function and for selectively enhancing CB2 actions in vivo. Our work will generate early candidates for the discovery and development of new therapeutic medications. In this renewal, we will elucidate the functional selectivity aspect of CB1 agonists and develop positive allosteric modulators at CB1 that selectively enhance endocannabinoid signaling. We also propose to develop highly selective CB2 agonists to enable studies of CB2 in vivo while limiting the contributions of CB1 that have been associated with undesirable side effects. Additionally, we propose to develop ligands that act as activators of CB2 while also acting as CB1 antagonists. Using such compounds in vivo may lay the groundwork for the development of medications for inflammatory and fibrotic disorders. Our goals will be accomplished through the synthesis of druggable analogs. The design of these ligands will be based on existing structures of the CB1 and CB2 receptors that were developed during the current funding period and by utilizing computational approaches. The work will require detailed molecular pharmacology aimed at studying the signaling of novel compounds accompanied by targeted mutations in CB1 and CB2 to confirm mechanistic underpinnings of pharmacological divergences in signaling. The most efficient novel compounds will be assayed using in vivo approaches aimed at exploring potential therapeutic value. The overall project will provide foundational information on cannabinoid receptor signaling and serve as a basis for the future development of rationally designed, mechanism-based therapeutic medications.