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The split-respiratory centre in the cat: responses to hypercapnia
Respiration Physiology
|August 1, 1984
Summary
Splitting the cat brainstem disrupts respiratory rhythm generation. However, medullary neurons and vagus nerves regain function during hypercapnia (high CO2), suggesting an increased CO2 threshold for respiratory control.
Area of Science:
- Neuroscience
- Respiratory Physiology
- Animal Models
Background:
- Respiratory rhythm generation is primarily controlled by the brainstem.
- The role of specific brainstem pathways in response to hypercapnia requires further elucidation.
Purpose of the Study:
- To investigate the impact of mid-sagittal brainstem splitting on respiratory neuron activity.
- To determine the response of phrenic motoneurons, efferent vagus nerve, and medullary respiratory neurons to hypercapnia in split-brainstem cats.
Main Methods:
- Cats were anesthetized, vagotomized, paralyzed, and artificially ventilated.
- The medulla was split in the midline.
- Responses to hypercapnia (5% CO2-oxygen mixture) and normocapnia were recorded.
Main Results:
- Mid-sagittal brainstem splitting abolished baseline electrical activities.
- Inhalation of a 5% CO2-oxygen mixture restored rhythmic firing in medullary units and efferent nerves at an average PaCO2 of 55 mm Hg (mean pH 7.20).
- Activity ceased upon return to normocapnia, with PaCO2 and pH returning to control levels.
Conclusions:
- Splitting the brainstem in cats affects respiratory rhythmogenesis.
- This procedure appears to increase the CO2 threshold of medullary respiratory neurons, impacting their response to hypercapnia.
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