Alimentary TractDistal and deglutitive inhibition in the rat esophagus: Role of inhibitory neurotransmission in the nucleus tractus solitarii☆,☆☆
Section snippets
Materials and methods
All procedures in this study were approved by the Animal Care Committee of Memorial University of Newfoundland in accordance with the Guidelines of the Canadian Council on Animal Care.
Motor and ventral medullary single unit responses to esophageal distention
In the distal esophagus, rhythmic pressure waves (mean frequency, 0.66 ± 0.03 Hz; n = 14) occurred during local distention at low to moderate volume (50–150 μL). Concurrent midthoracic esophageal distention invariably resulted in an instantaneous cessation of this rhythmic response (i.e., distal inhibition). Upon deflation of the proximal esophageal balloon, the distention-evoked rhythmic contractions resumed promptly. Bilateral cervical vagotomy (n = 5) eliminated distention-evoked reflex
Discussion
Although both distal and deglutitive inhibition of the esophagus have been extensively studied in humans3, 4, 5, 6, 7, 8 and laboratory animals,23, 24 information about the underlying neural mechanism(s) is still limited. Two recent studies in the opossum, which has a mixed striated and smooth muscle esophagus, suggest that deglutitive and distal inhibition are not the same25 and that the latter depends in part on a local intramural reflex using nitric oxide as the final mediator.26 In the rat,
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Supported by Medical Research Council of Canada. Dr. Dong holds a graduate fellowship from the Memorial University of Newfoundland.
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Address requests for reprints to: Detlef Bieger, M.D., Division of Basic Medical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John's, Newfoundland, Canada A1B 3V6. e-mail: [email protected]; fax: (709) 737-7010.