Carbon dioxide effects on olfactory functioning: behavioral, histological and immunohistochemical measurements

Area of Science:

• Toxicology
• Neuroscience
• Olfactory System Research

Background:

• Limited research exists on gaseous inhalation effects on olfactory functioning.
• Carbon dioxide (CO2) effects on general physiology are known, but its impact on olfactory neuroepithelium is less understood.

Purpose of the Study:

• To investigate the effects of 3% CO2 inhalation on mouse olfactory neuroepithelium.
• To compare the impacts of two exposure durations: 5 hours/day and 12 hours/day.

Main Methods:

• Mice were exposed to 3% CO2 for 5h/day or 12h/day.
• Behavioral, histological, and immunohistochemical analyses were performed bi-weekly.
• Quantification of olfactory marker protein (OMP) and proliferating cell nuclear antigen (PCNA) positive cells.

Main Results:

• Behavioral tests showed no effect on urine odor but increased repulsion to predator odor (TMT).
• Epithelium thickness decreased during and after exposure, with increased cell numbers.
• Mature olfactory neuron counts (OMP+) increased initially, then decreased with 12h/day exposure, but remained stable with 5h/day exposure.
• Proliferating cell nuclear antigen (PCNA+) positive cells consistently decreased.

Conclusions:

• CO2 inhalation effects on the olfactory system are dose-dependent, influenced by exposure duration.
• 5h/day CO2 exposure appears less detrimental to olfactory neuron maintenance than 12h/day exposure.