Selective manipulation of the function of nicotinic acetylcholine receptors (nAChRs) may be beneficial in the treatment of a variety of disorders that impact mental and neurological health, including mood disorders, Parkinson's Disease, cognitive disorders and chronic pain. A major thrust of current research is to identify the subunits in the different functional channel subtypes of nAChRs and to understand their roles in health and disease. The availability of selective probes for the nAChR subtypes will greatly facilitate these efforts, and provide a platform for development of medications capable of modulating specific nAChR-mediated functions in the nervous system. Venoms from carnivorous marine snails of the genus Conus are an extraordinarily rich source of compounds (alpha-conotoxins) that potently and selectively target specific nAChR subtypes. The aim of this proposal is to identify and characterize compounds from these venoms that discriminate among distinct acetylcholine-binding subunit interfaces of neuronal nAChRs. This aim will be accomplished by using receptor-based assays to track the purification of active venom compounds. Genes encoding alpha-conotoxins will also be cloned to isolate new toxins. Peptides identified by either approach will be biochemically characterized and synthesized. These peptides will then be fully characterized with respect to receptor subtype specificity. Subsequently, synthetic strategies will be utilized to develop second-generation ligands with refined specificity. Structure/function studies will determine critical receptor binding residues. Using a combination of approaches, including the use of selective conotoxin probes, the molecular composition of native receptors will be functionally and biochemically defined.