Contributions from rostral medullary nuclei to  coordination of swallowing and breathing in awake goats

The purpose of this study was to determine whether neurons in the facial (FN), gigantocellularis reticularis (RGN), and vestibular (VN) nuclei contribute to the regulation of breathing, swallowing, and the coordination of these two functions. Microtubules were chronically implanted bilaterally in goats. Two weeks later during wakefulness, 100-nl unilateral injections were made of mock cerebral spinal fluid or an excitatory amino acid receptor agonist or antagonists. When the agonist, N-methyl-d-aspartic acid, was injected into any nuclei, breathing and swallowing increased transiently (15–30%; P < 0.05), whereas only injections of the antagonist 2,3-dihydroxy-6-nitro-7-sulfamoylbenzo-(f)quinoxaline into VN increased swallowing (20%; P < 0.05). The phase of breathing in which the swallows occurred was not altered by any injections. However, more importantly, injections of the agonist and the antagonists significantly altered ( P < 0.05) by 5–50% the respiratory phase-dependent timing and tidal volume effect of swallows on breathing relative to mock cerebral spinal fluid injections. In addition, these effects were not uniform for all three nuclei. We conclude that the FN, RGN, and VN are part of a neural circuit in the rostral medulla that regulates and/or modulates breathing, swallowing, and their coordination in the awake state.

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Perturbations in three medullary nuclei enhance fractionated breathing in awake goats

Journal of Applied Physiology ◽

10.1152/japplphysiol.00837.2002 ◽

2003 ◽

Vol 94 (4) ◽

pp. 1508-1518 ◽

Cited By ~ 6

Author(s):

Thom R. Feroah ◽

H. V. Forster ◽

Carlo G. Fuentes ◽

Paul Martino ◽

M. Hodges ◽

...

Keyword(s):

Receptor Agonist ◽

Excitatory Amino Acid ◽

Respiratory Rhythm ◽

Upper Airway ◽

Rapid Eye Movement Sleep ◽

Excitatory Amino Acid Receptor ◽

Synaptic Inputs ◽

Medullary Nuclei ◽

Upper Airway Muscles ◽

Diaphragm Activity

Our aim was to determine the frequency and characteristics of a fractionated pattern of diaphragm and upper airway muscle activity and airflow during wakefulness and sleep in adult goats. A fractionated breath (FBr) was defined as three or more brief (40–150 ms) interruptions in the diaphragm activity not associated with multiple swallows, eructation, mastication, or movement. During a FBr, the discharge pattern in the diaphragm and upper airway muscles showed complete cycles of inspiration and expiration. Whereas the interval between peak diaphragm activity of the breath preceding the FBr to the first diaphragm peak of the FBr was 15–20% less than the average interval of the preceding five control breaths, the breath-to-breath interval of the five breaths after a FBr did not differ from the control breaths before the FBr event. In normal goats, FBr was evident in only 4 of 18 (22%) awake goats and in only one of these goats during non-rapid eye movement sleep. In 35 goats with implanted microtubules in the medulla, FBr were present in 14 (40%) goats. In these goats with FBr, 78% (11 of 14) had one or more implantations into or near the facial, vestibular, or raphe nuclei. The effect of perturbations in these nuclei is probably nonspecific, because injections into these nuclei with mock cerebrospinal fluid or excitatory amino acid-receptor agonist or antagonist produced both increases and decreases in the frequency of the FBr while not altering their characteristics. Finally, a swallow occurred at the termination or during the first breath after 60% of the FBr. We speculate that the FBr manifest 1) the disruption of a neuronal network, which coordinates breathing and other functions (such as swallowing), utilizing the same anatomic structures, and/or 2) transient changes in synaptic inputs that increase the rate of the normal respiratory rhythm generator or allow an ectopic, anomalous generator to become dominant.

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