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Effect of multiple denervations on the exercise hyperpnea in awake ponies
L G Pan1, H V Forster, R D Wurster
1Program in Physical Therapy, Marquette University, Milwaukee 53233, USA.
Journal of Applied Physiology (Bethesda, Md. : 1985)
|July 1, 1995
Summary
Carotid body denervation accentuates exercise hyperventilation in ponies. Combining denervations did not reveal redundancy, suggesting limited alternative control mechanisms for exercise breathing beyond carotid chemoreceptors.
Area of Science:
- Exercise physiology
- Respiratory control
- Autonomic nervous system
Background:
- Previous studies documented exercise hyperventilation responses to single denervations in ponies.
- Carotid body denervation (CBD) accentuates, hilar nerve denervation (HND) does not affect, and spinal ablation (SA) mildly attenuates exercise hyperventilation.
Purpose of the Study:
- To investigate potential redundancy in respiratory control during exercise in ponies.
- To determine if combined denervations (CBD, HND, SA) yield unpredictable ventilatory responses.
Main Methods:
- Treadmill exercise in ponies subjected to various combinations of carotid body denervation, hilar nerve pulmonary vagal denervation, and spinal cord ablation.
- Measurement of arterial PCO2 to assess ventilatory response during exercise.
Main Results:
- Combined CBD with HND or SA generally accentuated hypocapnia, as predicted by CBD alone.
- HND did not alter exercise PCO2 in CBD or SA ponies.
- Triple denervation (CBD, HND, SA) resulted in a greater exercise hyperventilation than predicted from individual lesions.
Conclusions:
- The study found no evidence of redundancy in exercise hyperpnea mechanisms, except for potential carotid chemoreceptor error sensing during hypercapnia.
- Findings suggest that carotid chemoreceptors play a critical role in regulating exercise ventilation in ponies.