Expression Patterns of Odorant Receptors and Response Properties of Olfactory Sensory Neurons in Aged Mice
Department of Neuroscience, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA
Correspondence to be sent to: Minghong Ma, Department of Neuroscience, University of Pennsylvania School of Medicine, 215 Stemmler Hall, 3450 Hamilton Walk, Philadelphia, PA 19104, USA. email: minghong{at}mail.med.upenn.edu
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Abstract |
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The sense of smell deteriorates in normal aging, but the underling mechanisms are still elusive. Here we investigated age-related alterations in expression patterns of odorant receptor (OR) genes and functional properties of olfactory sensory neurons (OSNs)—2 critical factors that define the odor detection threshold in the olfactory epithelium. Using in situ hybridization for 9 representative OR genes, we compared the cell densities of each OR in coronal nose sections at different ages (3–27 months). The cell density for different ORs peaked at different time points and a decline was observed for 6 of 9 ORs at advanced ages. Using patch clamp recordings, we then examined the odorant responses of individual OSNs coexpressing a defined OR (MOR23) and green fluorescent protein. The MOR23 neurons recorded from aged animals maintained a similar sensitivity and dynamic range in response to the cognate odorant (lyral) as those from younger mice. The results indicate that although the cell densities of OSNs expressing certain types of ORs decline at advanced ages, individual OSNs can retain their sensitivity. The implications of these findings in age-related olfactory deterioration are discussed.
Key words: aging, main olfactory epithelium, odorant responses, olfactory receptor, olfactory sensory neurons
1 These authors contribute equally
Accepted 17 August 2009