Olfactory transduction

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Olfactory transduction is a series of events in which odor molecules are detected by olfactory receptors and chemical signals are transformed into electrical signal to the brain where they are perceived as smells.[1]

Once ligands (odorant particles) bind to specific receptors on the external surface of cilia, olfactory transduction is initiated. In mammals, olfactory receptors have been shown to signal via G protein. This is a similar type of signaling of other known G protein-coupled receptors (GPCR). The binding of an odorant particle on an olfactory receptor activates a particular G protein (Gαolf), which then activates adenylate cyclase, leading to cAMP production. cAMP then binds and opens Cyclic nucleotide-gated ion channel. This opening allows for an influx of both Na+ and Ca2+ ions into the cell, thus depolarizing it. The Ca2+ in turn activates chloride channels, causing efflux of Cl, which results in a further depolarization of the cell.[2]

The odorant-activated cAMP cascade in the olfactory sensory neuron is subject to negative feedback regulation, like all other G-protein mediated pathways. This contributes to response deactivation and adaptation to stimulus.[1]

Individual odorants activate subsets of receptors. Receptors also have varying affinities for odorant molecules. In addition, higher concentrations of odorants elicit activity from greater a number of receptors than do lower concentrations. Thus, odor intensity as well as odor identity is represented by combination of a number of activated receptors.[3]


  1. ^ a b M. Ma (2007) Encoding olfactory signals via multiple chemosensory systems. Crit. Rev. Biochem. Mol. Bio. 42 (6): 463-480. PMID 18066954
  2. ^ A.Kato & K. Touhara (2009) Mammalian olfactory receptors: Pharmacology, G protein coupling and desensitization. Cel. Mol. Life Sciences. 66(23): 3743-3753. PMID 19652915
  3. ^ S. Chig-Ying, K. Menus, & J.R. Carlson (2009) Olfactory Perception: Receptors. Cells and Circuits. Cell 139(1): 45-59. PMID 19804753

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 This article incorporates public domain material from the U.S. National Cancer Institute document "Dictionary of Cancer Terms".