Naris occlusion alters the electro-olfactogram: evidence for compensatory plasticity in the olfactory system.

Unilateral naris occlusion (NO) has been widely used as a method of olfactory deprivation to study the role of stimulus-driven activity in olfactory development [P.C. Brunjes, Unilateral naris closure and olfactory system development, Brain Res. Rev. 19 (1994) 146-160]. Recent immunochemical studies of the olfactory epithelium (OE) following NO provide evidence for a previously unknown compensatory response to deprivation [D.M. Coppola, A. Waguespack, M. Reems, M.L. Butman, J. Cherry, Naris occlusion alters transductory protein immunoreactivity in olfactory epithelium, Histol. Histopathol. 21 (2006) 487-501; A. Waguespack, M. Reems, M.L. Butman, J. Cherry, D.M. Coppola, Olfactory receptor neurons have enhanced olfactory marker protein immunoreactivity in the nasal cavity ipsilateral to naris occlusion, Brain Res. 1044 (2005) 1-7]. To further investigate this phenomenon we measured electro-olfactograms (EOG) from the open and occluded OE of adult mice that had undergone NO as newborns. EOG waveforms from the open side OE of NO mice were indistinguishable from those obtained from untreated animals. However, amplitudes of EOGs from the occluded OE of NO mice were greater, on average, than those recorded at matched locations from the open side. This result was consistent across turbinates, odors, and all but the highest odor concentration. In addition, EOGs recorded from the occluded OE had significantly slower onset and recovery kinetics. Responses in a double-pulse protocol confirmed that the kinetics of the cellular or population processes that underlie the EOG are slowed by NO. These results provide the most direct support, to date, for compensatory plasticity in the olfactory system.