Nasal mucus contains cAMP and cGMP which are critical factors in preservation of normal olfaction

Abstract

Olfaction is a sensory modality comprised of a tripartite complex of physiological components – brain, nerves and receptors. However, the majority of pathological changes which inhibit olfaction relates not to changes in nerves or brain but to changes in presence and character of olfactory receptors. Olfactory receptors are unique organs. They do not possess blood vessels or lymphatics, do not exhibit mitosis and are constantly being remodeled. All growth and development of olfactory receptors depend upon stem cells which are stimulated by growth factors to supply the chemical moieties responsible for stem cell action. These growth factors are constituents of nasal mucus. Growth factors consist of a variety of chemical moieties which influence stem cell function and thereby olfactory receptor growth and development. Growth factors are funneled from multiple body organ systems into nasal mucus where they act to stimulate stem cells. cAMP and cGMP are major growth factors in nasal mucus. Inhibition of these or other growth factors in nasal mucus will inhibit olfactory function. X‐irradiation to the nasal cavity related to tumor treatment inhibits total nasal mucus production and thereby produces smell loss (hyposmia) by inhibiting growth factor secretion. Inhibition of cAMP, cGMP or any other growth factor component of nasal mucus such as carbonic anhydrase VI or thyroxine also inhibits stem cell stimulation of receptor growth and development. Olfactory end organs respond to these stimuli to create the complex cellular growth patterns which result in normal olfactory cellular development and thereby normal olfaction. Interference with secretion or synthesis of cAMP and cGMP in nasal mucus causes hyposmia whereas activation of secretion of these cyclases corrects hyposmia.