The olfactory organ of the lobster antenna is large and accessible for both biochemical and physiological work, and can easily be stimulated by water-borne odorants, making it a good model system for studying olfactory reception. It also is remarkable because it responds specifically to several molecules that also are known to have important actions in the brain, providing a model for biochemical receptor mechanisms in the central nervous system. This project addresses the novel question of how the medium around the receptor sites contributes to the biochemical reception of a stimulus. Such "perireceptor" mechanisms can include degradative enzymes, re-uptake of compounds by cells, modification of ion or protein content in the fluid surrounding the receptor, and the role of the cuticle in regulating stimulus access to the receptor. Biochemical, physiological, and anatomical approaches will be used to analyze the perireceptor environment and its effects on the cellular responses to olfactory stimuli. Results from this multidisciplinary study will be important not only to work on olfaction and olfactory behavior, but also to understanding cellular mechanisms in the mammalian brain, where similar chemical processes are known to function.