Diaphragm and lung afferents contribute to inspiratory load compensation in awake ponies.
Abstract: We determined the effect of pulmonary vagal (hilar nerve) denervation (HND) and diaphragm deafferentation (DD) on inspiratory load compensation. We studied awake intact (I; n = 10), DD (n = 5), HND (n = 4), and DD+HND (n = 7) ponies at rest and during mild (1.8 mph, 5% grade) and moderate (1.8 mph, 15% grade) treadmill exercise before, during, and after resistance of the inspiratory circuit was increased from approximately 1.5 to approximately 20 cmH2O.l-1.s. During the first loaded breath in I ponies at rest, inspiratory time (TI) increased, expiratory time decreased, and inspiratory drive increased. There were minimal changes after the first breath, and inspiratory minute ventilation (VI) and arterial PCO2 did not change (P > 0.10) from control values. On the first loaded breath during exercise, TI increased but inspiratory drive either did not change or decreased from control values. TI and drive increased after the first breath, but the increases were insufficient to maintain VI and arterial PCO2 at control levels. First-breath load compensation remained after DD, HND, and DD+HND, but after DD+HND tidal volume and VI were compensated 5-10% less (P < 0.05) than in I ponies. In all groups inspiratory drive, tidal volume, and VI were markedly augmented on the first breath after loading was terminated with a gradual return toward control. We conclude that diaphragm and pulmonary afferents contribute to but are not essential for inspiratory load compensation in awake ponies.
Publication Date: 1994-03-01 PubMed ID: 8005879DOI: 10.1152/jappl.1994.76.3.1330Google Scholar: Lookup
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- Journal Article
- Research Support
- U.S. Gov't
- Non-P.H.S.
- Research Support
- U.S. Gov't
- P.H.S.
Summary
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This research paper focused on understanding how the signals from the lungs and diaphragm (afferents) contributed to the compensation of increased breathing load in awake ponies. The experiment was conducted using healthy ponies, ponies with cut off signals from the diaphragm, ponies with cut off signals from lungs, and ponies with signals from both the lungs and diaphragm cut off. The study found that although these afferents contribute to breathing load compensation, they are not critical for it.
Research Methodology
- The experiment involved 26 awake ponies. These animals were divided into four groups: intact ponies (n=10), ponies with diaphragm deafferentation, DD (n=5), ponies subjected to pulmonary vagal or hilar nerve denervation, HND (n=4), and ponies with both diaphragm deafferentation and pulmonary vagal denervation, DD+HND (n=7).
- The ponies were studied at rest and during periods of mild and moderate treadmill exercise. This was done before, during, and after an increase in resistance of the inspiratory circuit was introduced, which surged from around 1.5 to approximately 20 cmH2O.l-1.s.
Results and Observations
- For intact ponies at rest, the first loaded breath led to an extension of inspiratory time (TI), a decrease in expiratory time, and an increase in inspiratory drive. However, these changes were minimal after the first breath, and their inspiratory minute ventilation (VI) and arterial PCO2 did not significantly vary from the control values.
- During the exercise, the first loaded breath resulted in an increase in TI. However, the inspiratory drive either did not change or decreased from the control values. TI and the drive increased after the first breath, but the increases could not maintain VI and PCO2 at control levels.
- First-breath load compensation was observed even after DD, HND, and DD+HND procedures. Nevertheless, in DD+HND ponies, the tidal volume and VI were compensated 5-10% lesser than in intact ponies.
- In all groups, after the load was removed, the inspiratory drive, tidal volume, and VI significantly increased on the first breath, slowly returning to control levels.
Conclusion
- From these observations, it was concluded that both diaphragm and pulmonary afferents contribute to inspiratory load compensation in ponies.
- Despite this, they are not considered essential for the compensation process. This study brought insights into the mechanisms behind the body’s response to increased inspiratory load, particularly in equines.
Cite This Article
APA
Forster HV, Lowry TF, Pan LG, Erickson BK, Korducki MJ, Forster MA.
(1994).
Diaphragm and lung afferents contribute to inspiratory load compensation in awake ponies.
J Appl Physiol (1985), 76(3), 1330-1339.
https://doi.org/10.1152/jappl.1994.76.3.1330 Publication
Researcher Affiliations
- Department of Physiology, Medical College of Wisconsin, Milwaukee 53226.
MeSH Terms
- Animals
- Carbon Dioxide / blood
- Diaphragm / innervation
- Electrodes, Implanted
- Electromyography
- Horses / physiology
- Lung / innervation
- Muscle Denervation
- Neurons, Afferent / physiology
- Physical Exertion / physiology
- Respiratory Function Tests
- Respiratory Mechanics / physiology
- Spinal Nerve Roots / physiology
- Vagotomy
Grant Funding
- HL-25739 / NHLBI NIH HHS
Citations
This article has been cited 4 times.- Tsai HW, Condrey J, Adams S, Davenport PW. The effect of tracheal occlusion on respiratory load compensation: changes in neurons containing inhibitory neurotransmitter in the nucleus of the solitary tract in conscious rats.. Respir Physiol Neurobiol 2014 Dec 1;204:138-46.
- Pate KM, Davenport PW. Tracheal occlusions evoke respiratory load compensation and neural activation in anesthetized rats.. J Appl Physiol (1985) 2012 Feb;112(3):435-42.
- Segizbaeva MO. Loading and unloading breathing during exercise: respiratory responses and compensatory mechanisms.. Eur J Med Res 2010 Nov 4;15 Suppl 2(Suppl 2):157-63.
- Kinkead R, Zhan WZ, Prakash YS, Bach KB, Sieck GC, Mitchell GS. Cervical dorsal rhizotomy enhances serotonergic innervation of phrenic motoneurons and serotonin-dependent long-term facilitation of respiratory motor output in rats.. J Neurosci 1998 Oct 15;18(20):8436-43.
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