Neurons in the dorsomedial medulla contribute to swallow pattern generation: Evidence of inspiratory activity during swallow

Abstract

Active contraction of the diaphragm and other inspiratory pump muscles during swallow create a negative thoracic pressure to improve the movement of the bolus (food/liquid) into the esophagus. We tested the hypothesis that dorsomedial medullary inspiratory neurons, including the nucleus tractus solitarius (NTS, pre-motor to the phrenic) would be active during swallow induced by oral water infusion. We recorded neurons in the NTS and medial reticular formation in anesthetized spontaneously breathing cats, and induced swallow by injection of water into the oropharynx. Our results indicate that: 1) a majority of inspiratory cells in the dorsomedial medulla are active during swallow, 2) expiratory neurons are present in the medial reticular formation (deeper to the NTS) in unparalyzed cats and a majority of these cells decreased firing frequency during swallow. Our findings suggest that the dorsomedial medulla is a source of inspiratory motor drive during swallow and that a novel population of breathing-modulated neurons that also are modulated during swallowing exist in the medial reticular formation in unparalyzed animals.

Why individuals with cerebral palsy are at higher risk for respiratory complications from COVID-19

“…Furthermore, adults with CP have a greater risk of respiratory disease than adults in the general population [17,18]. The DIAm plays a critical role in reducing susceptibility to respiratory infections in two ways: 1) during the pharyngeal phase of swallowing, the DIAm generates a large negative intrathoracic pressure necessary to propel a food bolus through the pharynx and into the esophagus, with failure resulting in aspiration; and 2) coughing and sneezing, where the DIAm contributes to increased intraabdominal pressure necessary to expel aspirates and phlegm from the airway [11,[19][20][21]. Therefore, we propose that we should educate families of children with CP that their child may also have an impaired cough, which can increase their child's susceptibility to respiratory complications.…”

“…[19]. Prior 221 to phrenic motor neuron and DIAm activation during 222 swallowing, there is increased activation of inspiratory 223 pre-motor neurons in the dorsal medulla of the brain in 224 anesthetized, spontaneously breathing cats [20]. Thus, 225 the negative intrathoracic pressure generated by the 226 DIAm contributes to the rapid movement of the bolus 227 of food or water from the mouth to the esophagus.…”

Sex-specific vagal and spinal modulation of breathing with chest compression

“…Additionally, they demonstrated that, as the rate of locomotion increases, muscle recruitment during yield also increases in amplitude and duration. During breathing, activity of diaphragm, parasternal, and external intercostal muscles steadily increases in amplitude to reach a maximum peak producing inspiratory airflow; this activity comprises the "I" phase (Fig 2) [56,57]. The I phase is immediately followed by the beginning of the E phase (termed E1 or post-I in the literature [58,59]), which starts with a decrementing diaphragm burst and is then followed by a period of diaphragm quiescence.…”

Coordination of airway protective behaviors and swallow: effects of afferent feedback and sex.

“…Motoneurons and interneurons may be involved in more than one activity such as swallow and breathing Pitts, Poliacek, Rose, Reed, Condrey, Tsai, Zhou, Davenport, & Bolser, 2018;Saito, Ezure, & Tanaka, 2002c) or swallow and mastication or swallow and chewing. During early states of asphyxia, respiratory-related muscles, also active during swallow, are recruited to increase respiratory effort in which respiratory drive exceeds swallow drive (Jean, 2001a).…”

“…During breathing diaphragm, parasternal and external intercostals activity steadily increases in amplitude to reach a maximum peak producing inspiratory airflow; this activity comprises the "I" phase ( Figure 4-2) (Pitts, Poliacek, Rose, Reed, Condrey, Tsai, Zhou, Davenport, & Bolser, 2018;Pitts, Rose, Poliacek, Condrey, Davenport, & Bolser, 2015)). The I phase is immediately followed by the beginning of the E phase (termed E1 or post-I in the literature (Bautista, Sun, & Pilowsky, 2014;Dutschmann, Jones, Subramanian, Stanic, & Bautista, 2014)), which starts with a decrementing diaphragm burst and is then followed by a period of diaphragm quiescence.…”