Discharge Patterns of Hypoglossal Motoneurons During Fictive Breathing, Coughing, and Swallowing

Abstract

. We performed a series of experiments to study the intracellular activity of 58 hypoglossal motoneurons (HMs) in decerebrate, paralyzed, and ventilated cats. Changes in membrane potentials (MP) and discharge activities were evaluated during fictive breathing (FB), swallowing (FS), and coughing (FC). FS and FC were elicited by electrical stimulation of the superior laryngeal nerves. FB, FS, and FC all exhibited characteristic discharge patterns of the phrenic, abdominal, pharyngeal branch of the vagus, and hypoglossal nerves. Thirty-nine HMs displayed respiratory modulation, and 19 were nonrespiratory modulated. Nine HMs did not exhibit MP changes during FB, FS, and FC. During FS, 49 HMs exhibited MP changes consisting of depolarization, hyperpolarization or hyperpolarization-depolarization. HMs involved in FS were either respiratory modulated (n ϭ 38) or not (n ϭ 11). Only 20 HMs displayed MP changes and/or discharge activity during FC. All but two HMs fired during the expiratory phase of FC or at the end of this reflex. All HMs involved in FC (n ϭ 20) were also modulated during both FB and FS. Our results suggest that the XII nucleus is functionally divided into common and distinct subsets of HMs based on their spontaneous activities and responses observed during FS and FC. The changes in MP and discharge frequencies observed during the three behaviors also suggest that HMs are driven by specific premotor neurons during FS, whereas a common premotor pathway is involved during FB and FC.

Correction of respiratory disorders in a mouse model of Rett syndrome

“…The tonic activity seen in HN is also likely to be expiratory in origin. Although HN is often described as having solely inspiratory activity, particularly from in vitro preparations, there is evidence that the output of this cranial nerve also contains expiratory motor activity especially in vivo (19)(20)(21). Thus, the in situ characterization of PN apnea in Mecp2 −/+ female mice reveals that three expiratory outputs-post-I in cVN, AbN, and expiratory component of HN-are tonic.…”

Study of the human hypoglossal nucleus: Normal development and morpho-functional alterations in sudden unexplained late fetal and infant death

“…The present study was performed with the purpose to deepen our knowledges by evaluating the development and the involvement in these pathologies even of the hypoglossal nucleus (HGN), a nucleus of the dorsal part of the medulla oblongata that, even if not generally included among the so defined vital centers, takes part in specific phases of breathing. In fact the hypoglossal neurons, besides to coordinate swallowing, chewing and vocalization, have been identified as having a peak of activity during inspiration [8][9][10].…”

Noeud vital for breathing in the brainstem: gasping—yes, eupnoea—doubtful

“…In terms of discharge pattern, those of the hypoglossal and facial nerve can be either incrementing or decrementing, depending upon species and experimental conditions. Activity of the recurrent laryngeal branch of the vagus, innervating the intrinsic abductor muscles of the larynx, is typically incrementing in neural inspiration (Hwang et al 1983;St John & Bledsoe 1985a;Bartlett 1986;Roda et al 2002;Berger & Sebe 2007;St John & Leiter in press).…”

“…Yet this coordination is not absolute as the cranial nerves can exhibit discharges that are not related to the cyclical periods of neural inspiration and expiration. Such non-respiratory discharges, which are especially prevalent in the hypoglossal, trigeminal and facial nerves, reflect their involvement in rhythmic activities such as mastication and deglutition (Widdicombe 1980;Baekey et al 2001;Roda et al 2002;Morris et al 2003;Gestreau et al 2005).…”