ABSTRACT
The olfactory mucosa, as well as the nasal respiratory mucosa, has a very high metabolic capacity for endogenous and exogenous, or xenobiotic, substrates. Olfactory tissue also has a high degree of inflammatory and immune responsiveness stimulated by contact with foreign substances, exfoliates in response to toxic insult, and regenerates to varying degrees following this exfoliation. The olfactory epithelium is unique in containing the only recognized mammalian neurons that regenerate from precursor basal cells. In addition, these neurons are unique in contacting the external environment with their dendritic processes while the axonal processes of the same cells synapse within the central nervous system (CNS) in the olfactory bulbs. The olfactory mucosa, therefore, represents a tissue where interactions are continually occurring between secretory processes, immune responses, neural signaling, and cell death and development. This chapter examines the basic structure and cell types of the olfactory mucosa and then focuses primarily on the enzymatic capacity of this tissue. The anatomical characteristics generally common to all species are outlined and followed by a brief discussion of interspecies variability in the magnitude, localization, or occurrence of these characteristics. The localization of nasal enzymes and their metabolic capacities are compared across several species. Finally, the potential for these enzymes to modulate the toxicity of inhalants and to influence odor signal detection is discussed.
