Cellular Physiology of Sensory Ion Channels

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DESCRIPTION (provided by applicant): The long-term objective of this proposal is to understand how our nervous system detects and processes information in our environment and transduces such environmental stimuli into electrochemical events. Our approach is to exploit the pharmacological power of natural plant products, specifically those that elicit irritation or discomfort, to uncover novel signaling mechanisms involved in the detection of noxious stimuli by neurons of the somatosensory nervous system. Indeed, this approach has proven to be extremely fruitful in the discovery and analysis of cell surface receptors and enzymes that are important for the detection and modulation of pain-producing stimuli, as illustrated by the use of plant-derived products such as aspirin, morphine, capsaicin, and menthol to discover cycloogenases, opiate receptors, and thermosensitive TRP channels, respectively. A major focus of this application is to determine how pungent isothiocyanate compounds from mustard plants (such as wasabi) excite sensory neurons by activating TRPA1, an excitatory channel on primary sensory neurons. It is currently unknown how these agents serve as selective agonists for the TRPA1 channel. We will use a combination of genetic, chemical, and electrophysiological methods to address this question, answers to which should provide significant insight into endogenous mechanisms that promote the activation and/or modulation of TRPA1. In addition to serving as a "wasabi receptor", TRPA1 may contribute to the mechanism whereby inflammatory products, such as bradykinin, histamine, or serotonin excite sensory neurons. Thus, another of our aims is to use cultured sensory neurons from normal and TRPA1-deficient mice to determine whether TRPA1 contributes to these excitatory actions and, if so, what cellular signaling mechanisms underlie this process. Finally, we are also proposing to examine effects of other natural products on cultured sensory neurons with the aim of developing novel pharmacological probes with which to discover or characterize important cellular signaling mechanisms that contribute to the detection or modulation of sensory stimuli. These studies may stimulate the design and development of novel analgesic agents for treating peripheral pain syndromes, such as arthritis or viral and diabetic neuropathies.