Ciliary neurotrophic factor-immunoreactivity in olfactory sensory neurons

Area of Science:

• Neuroscience
• Olfactory System Biology
• Cellular Biology

Background:

• Ciliary neurotrophic factor (CNTF) is known for neuroprotection, axonal regeneration, and synaptogenesis in the central nervous system (CNS).
• The olfactory system exhibits significant lifelong neuroplasticity, with high physiological concentrations of CNTF.

Purpose of the Study:

• To investigate the cellular localization of CNTF-immunoreactivity in the rat and mouse olfactory epithelium.
• To determine the functional status and synaptic connections of CNTF-immunoreactive olfactory sensory neurons (ONs).

Main Methods:

• Immunohistochemistry in rat and mouse olfactory epithelia.
• Reporter gene expression analysis in mice under the CNTF promoter.
• Assessment of apoptotic markers and response to chemical lesioning.
• Electron microscopy and 3D reconstruction of olfactory bulb glomeruli.

Main Results:

• Individual olfactory sensory neurons (ONs) showed intense CNTF-immunoreactivity in both species.
• CNTF-immunoreactive ONs were mature, functional (olfactory marker protein-positive, growth associated protein 43-negative), and not undergoing apoptosis.
• CNTF-immunoreactive ON axons formed typical synapses within specific olfactory bulb glomeruli.
• The number of CNTF-immunoreactive ONs and innervated glomeruli varied between species and individuals, with lower numbers in mice than rats.

Conclusions:

• CNTF-immunoreactivity is present in a subset of mature, functionally competent ONs in rodents.
• The precise glomerular targeting of CNTF-immunoreactive ON axons suggests a link to specific olfactory receptor protein expression or activation.