Characteristics of Olfactory Epithelium and Manipulations of Neural Functions in the Brain by the Intranasal Administration

Olfactory cells receive numerous odorants including toxic substances. To avoid complete loss of the olfactory function by toxic odorants, continuous neurogenesis of olfactory cells occurs even at adulthood. Newly generated olfactory neurons extend their axons to the olfactory bulb. Various molecules including polypeptides, proteins, polynucleotides, virus, and cells administrated intranasally have been reported to move from the olfactory epithelium to the brain tissue via the olfactory epithelium-olfactory bulb pathway. I discuss the pathway of substances intranasally administrated to the brain from the view point of characteristics of the olfactory epithelium.