Figure 1.

Olfactory signal transduction. A, Schematic drawing of the olfactory neuroepithelium. The epithelial surface is covered with mucus (MU) that forms the environment for the chemosensory cilia (CI) of OSNs. Epithelial supporting cells (SC) form the apical surface and maintain a regular pattern of dendritic knobs (DK), the apical endings of OSN dendrites. Basal cells (BC) are nondifferentiated neurons that continuously replace OSNs. The mucus layer is primarily supplied by Bowman's glands (BG). B, The current model of excitatory components in olfactory signal transduction. Odorants bind to olfactory receptor proteins (R), which induce activation of type III adenylyl cyclase (AC) through the G-protein G_olf. cAMP opens cyclic nucleotide-gated ion channel, leading to Ca²⁺ influx and activation of Ca²⁺-gated Cl^- channels.