Innervation of the Nose and Nasal Region of the Rat: Implications for Initiating the Mammalian Diving Response

Abstract

Most terrestrial animals demonstrate an autonomic reflex that facilitates survival during prolonged submersion under water. This diving response is characterized by bradycardia, apnea and selective increases in peripheral vascular resistance. Stimulation of the nose and nasal passages is thought to be primarily responsible for providing the sensory afferent signals initiating this protective reflex. Consequently, the primary objective of this research was to determine the central terminal projections of nerves innervating the external nose, nasal vestibule and nasal passages of rats. We injected wheat germ agglutinin (WGA) into specific external nasal locations, into the internal nasal passages of rats both with and without intact anterior ethmoidal nerves (AENs), and directly into trigeminal nerves innervating the nose and nasal region. The central terminations of these projections within the medulla were then precisely mapped. Results indicate that the internal nasal branch of the AEN and the nasopalatine nerve, but not the infraorbital nerve (ION), provide primary innervation of the internal nasal passages. The results also suggest afferent fibers from the internal nasal passages, but not external nasal region, project to the medullary dorsal horn (MDH) in an appropriate anatomical way to cause the activation of secondary neurons within the ventral MDH that express Fos protein during diving. We conclude that innervation of the anterior nasal passages by the AEN and nasopalatine nerve is likely to provide the afferent information responsible for the activation of secondary neurons within MDH during voluntary diving in rats.

Vagal Afferent Processing by the Paratrigeminal Nucleus

“…In guinea pigs, jugular vagal afferents evoke an apnea in anesthetized animals when stimulated and mediate coughing in response to inhaled noxious chemicals in conscious animals (Chou et al, 2008, 2018; Driessen et al, 2015, 2018). The apneic response, readily induced from the guinea pig larynx (Driessen et al, 2015, 2018), is perhaps consistent with the reported role of the paratrigeminal nucleus in the diving reflex whereby stimulation of trigeminal afferents in the nose promotes breath holding (Panneton et al, 2000; McCulloch et al, 2018). Indeed, the jugular vagal innervation to the larynx is particularly dense an either electrical stimulation or topically applied capsaicin evokes a profound withdrawal of respiratory drive.…”

Diving in the Arctic: Cold Water Immersion’s Effects on Heart Rate Variability in Navy Divers

“…The novelty of our study is the observation that in these freezing water conditions, after a quick increase at the beginning of the dives, parasympathetic (PNS) activity actually decreased for HRV measures at 5-0 min. The first PNS response (M1) could be explained with a strong diving reflex at the beginning of the dives (Konishi et al, 2016;Schaller et al, 2017;Vega, 2017;McCulloch et al, 2018;Schlader et al, 2018). The next measure (M2) may suggest that, in humans, the diving reflex-induced PNS response actually decreased after a while.…”

Features of hemodynamics of pulmonary circulation during the diving reflex

“…It is noted that pulmonary veins are a functional reservoir of blood for the cardiovascular system. Sympathetic vasoconstriction of the pulmonary veins can be essential for mobilizing a given volume of blood under general stress conditions of the cardiovascular system (Morman and Heller, 2000).…”