A significant component of the olfactory system's discriminative ability is thought to be that individual olfactory receptor neurons (ORNs) respond differently to different odorants. One study suggested this ability changes during development. Use of voltage sensitive dyes (VSDs) to monitor membrane potentials overcomes many of the problems that limited previous studies. We propose to use VSDs to assay ORN function in a culture system containing differentiating ORNs. Immunocytochemical identification of the ORN's differentiation state will allow correlation of each ORN's function with its maturity. We hypothesize a) most ORNs will respond to each odorant; b) a subpopulation of the mature ORNs will respond to lower concentrations of a given odorant than immature or other mature ORNs will; and c) certain aspects of this subpopulation's generator potentials will differ from those of other ORNs. These hypotheses agree with the following supposition; all ORNs respond to odorants via nonreceptor-mediated mechanisms; while mature ORNs use additional, receptor-mediated mechanisms.
The specific aims are to 1) characterize the immature, cultured ORNs' responses to odorants, and 2) characterize the mature, cultured ORNs' responses to odorants and compare them to those of immature ORNs. This VSD assay will aid the future correlation of each ORN's function with its odorant receptor genes. This work will lead to studies of the regulation of ORN differentiation and ultimately may increase out understanding of recovery from nervous system damage.
