Effect of multiple denervations on the exercise hyperpnea in awake ponies.
Abstract: In three previously reported studies, we had documented that the normal exercise hyperventilation in ponies is accentuated by carotid body denervation (CBD), not affected by hilar nerve pulmonary vagal denervation (HND), and mildly attenuated by spinal cord ablation of the dorsal lateral columns at L2 (SA). In the present study, we hypothesized that if redundancy of control existed in exercising ponies, then multiple denervations of theoretically important pathways in the same animal might attenuate the ventilatory response to exercise in a way not predictable by the individual lesion experiments alone. There were three major findings in the various combinations of CBD, HND, and SA in ponies during treadmill exercise. First, the combination of CBD with HND or SA resulted generally in an accentuation of the hypocapnia during exercise that was predictable on the basis of CBD alone. However, in one pony that showed a hypercapnic exercise response after SA alone, CBD subsequently caused a greater exercise hypercapnia. Second, HND in a CBD or SA pony did not affect the exercise arterial PCO2 response, which is consistent with previous data showing the lack of an HND effect in otherwise intact ponies. Third, in ponies with all three denervations together, the predominant response was an increase, not a decrease, in the exercise hyperventilation; this increase was greater than that predicted from the individual lesions. We conclude that these data do not provide evidence of redundancy in mechanism for the exercise hyperpnea other than instances of carotid chemoreceptor error sensing when hypercapnia occurs during exercise.
Publication Date: 1995-07-01 PubMed ID: 7559236DOI: 10.1152/jappl.1995.79.1.302Google Scholar: Lookup
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- Journal Article
- Research Support
- Non-U.S. Gov't
- Research Support
- U.S. Gov't
- Non-P.H.S.
- Research Support
- U.S. Gov't
- P.H.S.
Summary
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The research study investigates the effect of different nerve denervations on the ventilatory response of ponies during exercise. The results suggest that there is limited redundancy in mechanisms for exercise-induced hyperpnea beyond carotid chemoreceptor error sensing.
Study Hypothesis
- The investigators initially hypothesized that if there was a redundancy of control mechanisms in regulating breathing during exercise in ponies, this could be uncovered through multiple denervations of important pathways within the same animal. They thought that these denervations might impact the ventilatory response during exercise in a way not foreseeable through individual lesion experiments.
Methodology
- The study observed the effects of three types of denervations: carotid body denervation (CBD), hilar nerve pulmonary vagal denervation (HND), and spinal cord ablation of the dorsal lateral columns at L2 (SA).
- They combined these denervations in various ways in the studied ponies, and observed the animals’ responses during treadmill exercise.
Major Findings
- Firstly, when CBD was combined with HND or SA, it typically led to a deepened state of low carbon dioxide in the blood (hypocapnia) during exercise. This result was predictable based on the effects of CBD alone. However, in a pony that demonstrated an abnormal rise in carbon dioxide in the blood (hypercapnic) following SA alone, CBD caused a further increase in this hypercapnia during exercise.
- Secondly, HND did not impact the arterial PCO2 response during exercise in a pony already subjected to CBD or SA. This is congruent with older data showing that HND does not impact otherwise healthy ponies.
- Thirdly, when ponies had all three denervations together (CBD, HND, SA), the prevailing response was an increase, not a decrease, in the hyperventilation during exercise. This increase was greater than what was expected from the individual lesions.
Conclusions
- The study concludes that the findings do not provide evidence of redundancy in control mechanisms for exercise-induced hyperpnea. Exceptions to this may be instances involving carotid chemoreceptor error sensing when hypercapnia occurs during exercise.
Cite This Article
APA
Pan LG, Forster HV, Wurster RD, Brice AG, Lowry TF.
(1995).
Effect of multiple denervations on the exercise hyperpnea in awake ponies.
J Appl Physiol (1985), 79(1), 302-311.
https://doi.org/10.1152/jappl.1995.79.1.302 Publication
Researcher Affiliations
- Program in Physical Therapy, Marquette University, Milwaukee 53233, USA.
MeSH Terms
- Afferent Pathways / physiology
- Animals
- Carotid Body / physiology
- Denervation
- Horses / physiology
- Hyperventilation / etiology
- Hyperventilation / physiopathology
- Physical Exertion
- Spinal Cord / physiology
- Vagus Nerve / physiology
Grant Funding
- HL-25739 / NHLBI NIH HHS
- S32-H107354-01A1-CLN-2 / CLC NIH HHS
Citations
This article has been cited 3 times.- Smith CA, Forster HV, Blain GM, Dempsey JA. An interdependent model of central/peripheral chemoreception: evidence and implications for ventilatory control.. Respir Physiol Neurobiol 2010 Oct 31;173(3):288-97.
- Thornton JM, Guz A, Murphy K, Griffith AR, Pedersen DL, Kardos A, Leff A, Adams L, Casadei B, Paterson DJ. Identification of higher brain centres that may encode the cardiorespiratory response to exercise in humans.. J Physiol 2001 Jun 15;533(Pt 3):823-36.
- Paterson DJ. Potassium and breathing in exercise.. Sports Med 1997 Mar;23(3):149-63.
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