Chapter 18 - Intranasal Trigeminal Chemoreception

Abstract

The intranasal trigeminal system is a third chemical sense next to smell and taste. The trigeminal nerve’s free endings innervate the facial mucosa and the skin and convey sensory information arising from contact of a stimulus with the facial skin or the face’s mucosa. The activation of polymodal nociceptors via a ligand–receptor interaction induces distinct sensations in terms of touch, temperature, and nociception. Despite the trigeminal system’s critical role as a sentinel in protecting the individual from harmful substances, our knowledge of the intranasal trigeminal chemosensory system and its relationship with olfaction is far from complete. We know that the majority of odorants has the ability to stimulate both the olfactory and the trigeminal nerves, at least at high concentration levels. In addition to the overlap observed at the stimulus level, there are complex interactions between both at sensory systems occurring in the periphery (ie, on mucosal levels) and at central levels (ie, in the central nervous systems). Different factors affect sensitivity for trigeminal chemosensory perception: aging, sex, olfactory status, or specific diseases are considered determinant factors.