The Journal of Neuroscience, January 1, 2003, 23(1):317-324
Olfactory Signal Transduction in the Mouse Septal Organ
Minghong
Ma1,
Xavier
Grosmaitre1,
Carrie
L.
Iwema2,
Harriet
Baker3,
Charles A.
Greer1, 2, and
Gordon M.
Shepherd1
Departments of 1 Neurobiology and
2 Neurosurgery, Yale Medical School, New Haven, Connecticut
06520, and 3 Weill Medical College, Cornell University,
White Plains, New York 10605
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 ~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.
Key words:
septal organ; main olfactory epithelium; signal
transduction; cAMP pathway; adenylyl cyclase III; Golf; guanylyl cyclase-D; phosphodiesterase 2; olfactory sensory neuron
Copyright © 2003 Society for Neuroscience 0270-6474/03/231317-08$05.00/0
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