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Ventilatory afterdischarge in the awake goat
M J Engwall1, L Daristotle, W Z Niu
1Department of Comparative Biosciences, University of Wisconsin, Madison 53706.
Journal of Applied Physiology (Bethesda, Md. : 1985)
|October 1, 1991
Summary
Ventilatory afterdischarge (VAD) was observed in awake goats, demonstrating this respiratory phenomenon in a new model. Maintaining stable carbon dioxide levels (isocapnia) is crucial for observing VAD.
Area of Science:
- Respiratory Physiology
- Neuroscience
- Animal Models
Background:
- Ventilatory afterdischarge (VAD) is a sustained increase in breathing after stimulus removal, previously shown in anesthetized animals.
- The carotid sinus nerve and carotid body are key respiratory control sites influencing ventilation.
Purpose of the Study:
- To investigate the existence of VAD in standing, awake goats.
- To assess the role of carotid body stimulation in VAD.
- To determine the impact of arterial carbon dioxide levels on VAD manifestation.
Main Methods:
- Seven awake goats were studied using an extracorporeal circuit for controlled carotid body stimulation.
- Square-wave stimulation of the carotid chemoreceptor was applied.
- Ventilatory parameters (minute ventilation, tidal volume, respiratory frequency) and arterial PCO2 were monitored.
Main Results:
- Ventilatory afterdischarge was successfully demonstrated in awake goats following carotid body stimulation.
- Time constants for diminishing ventilation, tidal volume, and frequency were calculated (27.7, 34.5, and 25.5 s, respectively).
- Maintaining isocapnia (stable arterial PCO2) was essential; decreases in PCO2 significantly attenuated VAD magnitude and duration.
Conclusions:
- The awake goat serves as a viable model for studying ventilatory afterdischarge.
- Carotid body stimulation can elicit VAD in awake animals.
- Isocapnia is a critical determinant for observing VAD, highlighting the interplay between chemoreception and CO2 homeostasis.