title: Olfactory signal transduction in the mouse septal organ.
abstract: The septal organ, a distinct chemosensory organ observed in the mammalian nose, is essentially a small island of olfactory neuroepithelium located bilaterally at the ventral base of the nasal septum. Virtually nothing is known about its physiological properties and function. To understand the nature of the sensory neurons in this area, we studied the mechanisms underlying olfactory signal transduction in these neurons. The majority of the sensory neurons in the septal organ express olfactory-specific G-protein and adenylyl cyclase type III, suggesting that the cAMP signaling pathway plays a critical role in the septal organ as in the main olfactory epithelium (MOE). This is further supported by patch-clamp recordings from individual dendritic knobs of the sensory neurons in the septal organ. Odorant responses can be mimicked by an adenylyl cyclase activator and a phosphodiesterase inhibitor, and these responses can be blocked by an adenylyl cyclase inhibitor. There is a small subset of cells in the septal organ expressing a cGMP-stimulated phosphodiesterase (phosphodiesterase 2), a marker for the guanylyl cyclase-D subtype sensory neurons identified in the MOE. The results indicate that the septal organ resembles the MOE in major olfactory signal transduction pathways, odorant response properties, and projection to the main olfactory bulb. Molecular and functional analysis of the septal organ, which constitutes approximately 1% of the olfactory epithelium, will provide new insights into the organization of the mammalian olfactory system and the unique function this enigmatic organ may serve.
authors.affiliation: Department of Neurobiology, Yale Medical School, New Haven, Connecticut 06520, USA. mma@mail.med.upenn.edu
authors.forename: Minghong
authors.initials: M
authors.lastname: Ma
authors.forename: Xavier
authors.initials: X
authors.lastname: Grosmaitre
authors.forename: Carrie L
authors.initials: CL
authors.lastname: Iwema
authors.forename: Harriet
authors.initials: H
authors.lastname: Baker
authors.forename: Charles A
authors.initials: CA
authors.lastname: Greer
authors.forename: Gordon M
authors.initials: GM
authors.lastname: Shepherd
mesh_terms: D000262:Adenylyl Cyclases / Q000032:analysis / Q000276:immunology; D000818:Animals; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism*; D054678:Cyclic Nucleotide Phosphodiesterases, Type 2; D004553:Electric Conductivity; D005260:Female; D006162:Guanylate Cyclase / Q000378:metabolism; D007150:Immunohistochemistry; D007527:Isoenzymes / Q000032:analysis / Q000276:immunology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008959:Models, Neurological; D009831:Olfactory Mucosa / Q000166:cytology; D009833:Olfactory Pathways / Q000166:cytology; D018034:Olfactory Receptor Neurons / Q000166:cytology / Q000378:metabolism* / Q000502:physiology; D018408:Patch-Clamp Techniques; D010727:Phosphoric Diester Hydrolases / Q000032:analysis; D000074261:Receptors, Enterotoxin; D050705:Receptors, Guanylate Cyclase-Coupled; D018000:Receptors, Peptide / Q000378:metabolism; D015290:Second Messenger Systems
chemical_list: D007527:Isoenzymes; D018000:Receptors, Peptide; D000242:Cyclic AMP; D010727:Phosphoric Diester Hydrolases; D054678:Cyclic Nucleotide Phosphodiesterases, Type 2; C517277:Pde2a protein, mouse; D000262:Adenylyl Cyclases; C421784:adenylate cyclase 3; D006162:Guanylate Cyclase; D000074261:Receptors, Enterotoxin; D050705:Receptors, Guanylate Cyclase-Coupled