Naris occlusion alters transductory protein immunoreactivity in olfactory epithelium

We have recently shown that unilateral naris occlusion (UNO) causes an increase in olfactory marker protein (OMP) immunoreactivity (IR) in mouse olfactory sensory neurons (OSN) from the occluded side of the nasal cavity and a decrease in OMP-IR on the non-occluded side, relative to controls. Given OMP's demonstrated role in olfactory modulation, these OMP-IR changes have been interpreted as a compensatory response by OSNs to odor deprivation on the occluded side and to supernormal exposure to odor on the non-occluded side of the nasal cavity. In the current study, we examined the developmental timing and the regional distribution of this process throughout the nasal cavity using immunocytochemistry. Results demonstrate that OMP-IR diverges in OSNs from the occluded side relative to the non-occluded side of the nasal cavity within eleven days after UNO, with statistically significant differences measurable after 17 days (n=16). We also measured relative levels of the Type 4 phosphodiesterase (PDE4A), another potential olfactory modulator, in nasal cavity tissue from UNO (n=8) and untreated mice (n=9) using western blots and immunocytochemistry. Like OMP, PDE4A-IR increased on the occluded side of the nasal cavity after UNO. Finally, we used immunocytochemistry to assess relative levels of olfactory-specific adenylyl cyclase (ACIII, n=4) and G-protein (Golf, n=2) in OSNs from the occluded and non-occluded sides of the nasal cavity of UNO mice. Following UNO, ACIII but not Golf -IR levels diverged comparing the occluded to the non-occluded sides of the nasal cavity. Taken together, our findings provide support for the previously unknown phenomenon of compensatory responses by OSNs to odor environment.