The sense of smell, olfaction, depends on receptor nerve cells in the sensory tissue of the nose, which carry information to the brain. This information is encoded in the pattern of physiological activity of the receptor cells. Receptor cells have molecules on their surfaces that bind to odorant stimuli when present. It remains unknown, however, which odors are recognized by each of the olfactory receptors. This question of the molecular code for olfaction is a central question in olfactory research. This study approaches the issue with a powerful combination of voltage-sensitive dyes and molecular tagging, using the salamander nose as a model system having a relatively flat sheet of sensory tissue with limited numbers of receptor types. Physiological responses are localized by voltage-sensitive dyes at a cellular level of resolution, to identify which cells respond to particular odors. For the same tissue, molecular probes specific for olfactory receptor molecules are then used to histochemically label cells with particular receptors. Results showing which cells have types of response specificity matching up with particular receptor molecules will provide direct evidence to determine how a code for olfaction can be created. The potential impact of this work is very high for chemosensory sciences because how organisms recognize molecules in the environment is crucial for a variety of behaviors; the basic findings on molecular recognition also will be pertinent for understanding molecular recognition mechanisms in other sensory systems and in other parts of the brain.
