Reflex inhibition of crural diaphragmatic activity by esophageal distention in cats

• Published in: Respiration physiology Vol. 77; no. 2; pp. 195 - 202
• Main Authors: Oyer, Linda M., Knuth, Susan L., Ward, Dale K., Bartlett, Donald
• Format: Journal Article
• Language: English
• Published: Shannon Elsevier B.V 01.08.1989; Amsterdam Elsevier
• Subjects: Animals; Biological and medical sciences; Cardiorespiratory control. Arterial mecano- and chemoreceptor; Cats; Costal diaphragm; Crural diaghragm; Diaphragm - innervation; Diaphragm - physiology; Dorsal root; Electromyography; Esophageal distention; Esophagus - innervation; Esophagus - physiology; Fundamental and applied biological sciences. Psychology; Muscles - innervation; Muscles - physiology; Neural Pathways - physiology; Phrenic nerve; Phrenic Nerve - physiology; Respiration; Vagus nerve; Vagus Nerve - physiology; Vertebrates: respiratory system; Dorsal root; Costal diaphragm; Vagus nerve; Phrenic nerve; Esophageal distention; Crural diaghragm; Peripheral nervous system; Fissipedia; Inspiration; Carnivora; Nervous control; Digestive system; Electrophysiology; Vagotomy; Esophagus; Parasympathic nervous system; Vertebrata; Abdominal distension; Mammalia; Respiratory muscle; Autonomic nervous system; Cat; Cranial nerve; Electromyography; Diaphragm; Sensorimotor nerve; Respiration
• ISSN: 0034-5687
• DOI: 10.1016/0034-5687(89)90006-6

Distention of the esophagus has been shown to result in selective inhibition of phasic inspiratory activity in the crural portion of the diaphragm, with no effect on costal diaphragmatic activity. The purpose of this study was to determine rigorously the afferent pathways that mediate this response. Bipolar EMG electrodes were placed in the costal and crural portions of the diaphragm in decerebrate, spontaneously breathing cats. Distention of the esophagus by inflation of a Foley catheter balloon with 20 ml of air resulted in a selective inhibition of crural hiatal EMG activity, while costal EMG activity was maintained at predistention levels. The distention was accompanied by a reduction in respiratory frequency. Transection of the spinal cord at the C 8-T 1 level did not obliterate the crural inhibition produced by inflation. Section of the C 4-C 8 dorsal roots also failed to abolish the response. However, after bilateral cervical vagotomy, esophageal distention no longer influenced diaphragmatic EMG activity. These results indicate that the crural inhibition observed with esophageal distention is vagally mediated and is not influenced importantly by intercostal or phrenic afferents. Records of activity of the phrenic nerve branch innervating the crural portion of the diaphragm showed a similar response pattern, confirming that the inhibition is central in origin and that the crural fibers inhibited by distention are only a fraction of the total population of crural phrenic motoneurons.