Secretagogin expression in the mouse olfactory bulb under sensory impairments

Area of Science:

• Neuroscience
• Olfactory System Biology
• Cellular Neuroscience

Background:

• Olfactory bulb (OB) interneurons utilize calcium-binding proteins with incompletely understood functions.
• Secretagogin (SCGN) is a recently discovered calcium-binding protein expressed in OB interneurons.
• The specific role of SCGN-positive interneurons in olfactory processing remains unknown.

Purpose of the Study:

• To investigate the distribution, generation, and activity of SCGN-positive interneurons in the olfactory bulb.
• To analyze SCGN-positive interneuron responses in models of olfactory impairment: Purkinje Cell Degeneration (PCD) and olfactory deprivation.
• To elucidate the functional significance of SCGN in the olfactory pathway.

Main Methods:

• Comparative analysis of SCGN-positive cell density in olfactory-deprived and control mice.
• Bromodeoxyuridine (BrdU) labeling to assess cell proliferation of SCGN-positive interneurons.
• C-Fos expression analysis to estimate neuronal activity in SCGN-positive interneurons in both olfactory-deprived and PCD models.

Main Results:

• A significant increase in SCGN-positive cell density was observed in the inframitral layers of olfactory-deprived mice.
• BrdU analysis indicated that the increased SCGN-positive cells were not newly generated, suggesting a change in existing cells.
• Neuronal activity, measured by c-Fos expression, increased in pre-existing SCGN-positive interneurons in both olfactory-deprived and PCD mice, with higher activity in PCD models.

Conclusions:

• The olfactory bulb exhibits distinct compensatory mechanisms in response to different types of olfactory alterations.
• SCGN expression is modulated by olfactory stimuli, indicating its involvement in sensory input regulation.
• SCGN-positive interneurons likely play a compensatory role against reduced sensory input, contributing to olfactory pathway adaptation.