Functional and Molecular Characterization of Individual Olfactory Neurons

Abstract: To gain an understanding of the olfactory signal transduction process, individual chemosensory neurons have been assessed for odor-induced Ca²⁺ responses and the molecular elements of transduction cascades using Ca²⁺ imaging technique in combination with single-cell RT-PCR approaches. It has been demonstrated that responsiveness of cells to cyclic AMP or inositol trisphosphate odorants was blocked by specific adenylyl cyclase inhibitors or phospholipase C inhibitors, respectively. Using specific primers in single-cell RT-PCR analysis, olfactory marker protein, two G protein subtypes (G_olf and G_o), and adenylyl cyclase (subtype III) and a phospholipase C (phospholipase Cβ₂-related subtype) were identified. For a subpopulation of sensory neurons it was demonstrated that both transduction cascades coexist and are active in the same cell. These data support the notion that two second messenger pathways are active in olfactory sensory neurons and emphasize the concept of dual transduction cascades in olfaction.