Distribution of Fos-Like Immunoreactivity, Catecholaminergic and Serotoninergic Neurons Activated by the Laryngeal Chemoreflex in the Medulla Oblongata of Rats

Abstract

The laryngeal chemoreflex (LCR) induces apnea, glottis closure, bradycardia and hypertension in young and maturing mammals. We examined the distribution of medullary nuclei that are activated by the LCR and used immunofluorescent detection of Fos protein as a cellular marker for neuronal activation to establish that the medullary catecholaminergic and serotoninergic neurons participate in the modulation of the LCR. The LCR was elicited by the infusion of KCl-HCl solution into the laryngeal lumen of adult rats in the experimental group, whereas the control group received the same surgery but no infusion. In comparison, the number of regions of Fos-like immunoreactivity (FLI) that were activated by the LCR significantly increased in the nucleus of the solitary tract (NTS), the vestibular nuclear complex (VNC), the loose formation of the nucleus ambiguus (AmbL), the rostral ventral respiratory group (RVRG), the ventrolateral reticular complex (VLR), the pre-Bötzinger complex (PrBöt), the Bötzinger complex (Böt), the spinal trigeminal nucleus (SP5), and the raphe obscurus nucleus (ROb) bilaterally from the medulla oblongata. Furthermore, 12.71% of neurons with FLI in the dorsolateral part of the nucleus of the solitary tract (SolDL) showed tyrosine hydroxylase-immunoreactivity (TH-ir, catecholaminergic), and 70.87% of neurons with FLI in the ROb were serotoninergic. Our data demonstrated the distribution of medullary nuclei that were activated by the LCR, and further demonstrated that catecholaminergic neurons of the SolDL and serotoninergic neurons of the ROb were activated by the LCR, indicating the potential central pathway of the LCR.

Central mechanisms of airway sensation and cough hypersensitivity

“…These data clearly argue for two anatomically distinct airway sensory processing pathways that may form an anatomical framework for functional distinctions between respiratory reflex production and the conscious perception of airway irritations. For example, reflexive cough is a brainstem-mediated process that requires sensory input into the nTS and subsequent alterations to the activity of respiratory cells located in nuclei of the ventral and pontine respiratory groups (Baekey et al, 2003, Poliacek et al, 2009, Mazzone et al, 2011, Smith et al, 2013, Dutschmann et al, 2014, Koshiya et al, 2014, Zoccal et al, 2014, Ferreira et al, 2015, Wang et al, 2015. On the other hand, the central mechanisms that underpin the conscious perception of airway sensations leading to voluntary respiratory behaviours are less well understood and could conceivably be linked to the understudied somatic representation of airway sensation in the brain that is seemingly carried by the jugular-Pa5 circuitry.…”

Medullary tyrosine hydroxylase catecholaminergic neuronal populations in sudden unexpected death in epilepsy

“…Following experimental seizures, c‐fos immunoreactivity in TH‐IR neurones in the VLM and dorsal vagal complex mirrored that observed following hypoxia (17) and was similar to the distribution following experimentally induced hypotension; this could suggest that seizures themselves directly induce TH neuronal activity. C‐fos expression was also noted in NTS and VLM TH and serotonergic neurones following induction of the protective laryngeal chemoreflex which induces respiratory inhibition, bradycardia, and hypertension (44). A previous post‐mortem study of sudden unexplained death, showed c‐fos‐expressing neurones in the dorsal medulla (hypoglossal nucleus and/or the dorsal vagal nucleus) but not in control groups (13).…”

Laryngeal Mask Ventilation during Tracheostomy Improves Intraoperative Hemodynamic Stability in Patients Undergoing Total Laryngectomy

“…We hypothesized that involvement of the laryngeal chemorefl ex would explain the reported results. This refl ex induces specifi c response initiated by receptors in the laryngeal lumen and among its numerous eff ects, a signifi cant increase in blood pressure has been attributed to it [9,10,11,12]. Presumably, during intubation in patients with advanced laryngeal cancer, there is a signifi cant mechanical compression on the endolarynx and respectively, on the tumor mass, because of the obstructed lumen, which could cause an induction of the laryngeal chemorefl ex.…”