Emetic stimulation inhibits the swallowing reflex in decerebrate rats

• Published in: Autonomic neuroscience Vol. 140; no. 1; pp. 24 - 29
• Main Authors: Kurozumi, Chiharu, Yamagata, Ryuzo, Himi, Naoyuki, Koga, Tomoshige
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01-06-2008; Elsevier
• Subjects: Advanced Basic Science; Animals; Biological and medical sciences; Decerebrate State; Deglutition - drug effects; Deglutition - physiology; Electric Stimulation; Electromyography; Emetic drug; Emetics - pharmacology; Fundamental and applied biological sciences. Psychology; Gagging - drug effects; Gagging - physiology; Gastric distension; Hypoxia; Laryngeal Muscles - innervation; Laryngeal Muscles - physiopathology; Laryngeal Nerves - physiology; Lithium Chloride - pharmacology; Medical Education; Medulla Oblongata - physiology; Muscle Contraction - drug effects; Muscle Contraction - physiology; Nerve Net - physiology; Peripheral nervous system. Autonomic nervous system. Neuromuscular transmission. Ganglionic transmission. Electric organ; Pharynx - innervation; Pharynx - physiology; Physical Stimulation; Rats; Rats, Sprague-Dawley; Reflex - drug effects; Reflex - physiology; Solitary Nucleus - drug effects; Solitary Nucleus - physiology; Stimulation, Chemical; Stomach - innervation; Stomach - physiology; Swallowing reflex; Vertebrates: nervous system and sense organs; Vomiting - chemically induced; Hypoxia; Gastric distension; Swallowing reflex; Emetic drug; Reflex; Stomach; Oxygen; Rat; Digestive system; Rodentia; Environmental factor; Stimulation; Swallowing; Vertebrata; Mammalia; Autonomic nervous system; Animal
• ISSN: 1566-0702; 1872-7484
• DOI: 10.1016/j.autneu.2008.02.001

Abstract The effects of emetic stimulation on the swallowing reflex were investigated in decerebrated rats. Hypoxia, gastric distension and LiCl administration were used as emetic stimulations. The swallowing reflex was elicited by electrical stimulation of the superior laryngeal nerve (SLN, 20 Hz, 3–5 V, 0.3 ms duration) for 20 s. To examine the effect of hypoxia, nitrogen gas was inhaled under artificial ventilation. There were significantly fewer swallows during a decrease in PO2 than under air ventilation ( p < 0.05). The number of swallows during 3-ml stomach distension was significantly lower than that before distension ( p < 0.05). Intravenous administration of LiCl (100 mg/kg) also significantly reduced the number of swallows ( p < 0.05). The combination of SLN stimulation and emetic stimuli occasionally produced burst activity of abdominal muscles, which might be associated with the gag reflex. Both the gag and swallowing reflexes are well known to be mediated by the nucleus of the solitary tract. The physiological roles of the gag reflex and the swallowing reflex are considered to be reciprocal. Taken together, these results suggest that emetic stimulation inhibits the swallowing pattern generator via the nucleus of the solitary tract, which in turn facilitates the gag reflex.