Chemical sensory systems detect a wide variety of chemicals in the external environment and provide sensory information that is essential for animals to identify food, predators and mates, and to avoid toxic environment. We are interested in chemical sensations mediated by olfactory and trigeminal systems in the nose cavity. We use a number of techniques, including electrophysiology, Ca2+ imaging, immunocytochemistry, molecular biology in normal and genetically modified mice to study sensory signal mechanisms in these two systems.
Pheromone signaling in the main olfactory system
The olfactory system is capable of detecting and discriminating thousands of airborne odorants and pheromones with exquisite sensitivity. Pheromones are chemicals that are released from animals and act on members of the same species, stimulating hormonal changes and instinctive behaviors. Recent studies have discovered pheromones can be detected by sensory neurons in both main and accessory olfactory systems in mice. We are particularly interested in pheromone signal processes in the main olfactory system. We have found a new signaling component TRPM5, a transient receptor potential channel in a subset of olfactory sensory neurons. We are now investigating functional roles of TRPM5 in signal transduction of pheromones and other biologically relevant odorants.
Chemical sensing in trigeminal system
The trigeminal system also detects chemical stimuli. Unlike the olfactory system, stimulation of trigeminal system by irritants, including strong odorants triggers protective reflexes that include sneezing, coughing and changing in respiration. Irritants can interact with trigeminal free nerve endings or solitary chemosensory cells, which then transmit sensory information onto the trigeminal nerve. Using immunolabeling and transgenic mice, we found a large population of solitary chemosensory cells in both respiratory and olfactory epithelia expressing the TRPM5, indicating multiple roles of TRPM5 in chemical sensing. Our initial study also indicated that some of the TRPM5-expressing cells respond to odorous irritants. We are investigating chemical specificity, signal transduction mechanisms and modulations in these solitary chemosensory cells.