The pathophysiology of pain remains poorly understood and there is clearly a need for new analgesics. ASICs (Acid-Sensing Ion Channels) have emerged as important players in the pain pathway. They form depolarizing cation channels activated by extracellular protons that are expressed in both sensory and central neurons. Our project aims to provide a better understanding of the mechanisms of pain by exploring with innovative pharmacological tools the role of ASICs in these processes, and to provide at the same time leads in the development of new analgesics. We will use the complementary expertises of the two partners, i.e., ASICs, electrophysiology, toxins and pain behaviour (Team#1), animal pain models and behaviour (Team#2) to achieve the following objectives: 1 – Better characterize the in vivo effects on chronic pain of mambalgins and develop from animal venoms new specific peptide blockers of ASICs with therapeutic potential. Take advantage of these toxins to investigate the structure-function of ASIC channels. Mambalgins are snake peptides recently identified by Team#1 in collaboration with Team#2 that block subtypes of central and peripheral ASIC channels to produce a potent analgesic effect in rodents in acute pain and inflammation. We propose to further characterize the in vivo analgesic activity of these peptides by exploring their effect via different delivery routes (i.t., i.c.v., i.pl., i.v.) on a variety of chronic pain models of clinical relevance like monoarthritis, neuropathy and migraine. We propose in parallel to screen animal venoms for new peptide toxins against ASIC channels lacking a specific pharmacology and/or of potential clinical interest. The most interesting ones will be patented and licensed for further clinical development. In addition, analysis of the interaction of the toxins with the targeted channels and of their mechanisms of inhibition will help to better understand the relationship between ASIC channel structure and function. 2 – Combine toxins with the other available tools to explore the pathophysiological role of ASIC channels in the peripheral and the central nervous system in inflammatory and neuropathic pain. We have previously shown the importance for inflammatory pain of peripheral ASIC channels in sensory neurons. However, a lot still remains to be understood in the regulation of these channels. We propose to explore the role of peripheral ASICs expressed in nociceptors in a context of inflammation and inflammatory pain by identifying new and/or pathology-specific modulators of these channels, and by evaluating the contribution of ASICs to the in vivo effects of these modulators. We will combine studies of the sensitivity of recombinant and native ASIC channels to specific inflammatory mediators (candidate approach) with a global translational approach through the effect of whole human inflammatory exudates isolated from different pathological conditions. The role of central and peripheral ASIC channels in neuropathic pain has never been directly investigated. We propose to take advantage of the specific toxin inhibitors already available and developed in the course of this project, as well as of ASIC-deficient and ASIC knockdown animals to study this role in two models of neuropathic pain of different aetiology (oxaliplatin-induced neuropathy and chronic constriction injury of sciatic nerve).