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Methacholine-induced bronchoconstriction and phrenic motoneuron activity in dogs
1Department of Physiology, National Yang-Ming Medical College, Taipei, Taiwan, Republic of China.
Respiration Physiology
|November 1, 1991
Summary
Changes in lung mechanics affect phrenic motoneuron firing via vagal reflexes. Late-onset motoneurons (LOM) are crucial for this response, adjusting their firing patterns during inspiration.
Area of Science:
- Respiratory Physiology
- Neuroscience
- Pulmonary Mechanics
Background:
- Phrenic motoneuron activity is vital for breathing.
- Bronchomotor tone influences respiratory mechanics.
Purpose of the Study:
- To investigate how bronchoconstriction affects phrenic motoneuron firing patterns.
- To identify the role of specific motoneuron types and vagal reflexes in this response.
Main Methods:
- Studied phrenic nerve efferent activity in anesthetized dogs.
- Induced bronchoconstriction using methacholine (MCh) aerosol.
- Recorded single phrenic motoneuron firing patterns and whole nerve activity.
Main Results:
- Methacholine increased total lung resistance and altered pulmonary mechanics.
- Phrenic nerve activity increased, primarily due to recruitment of late-onset motoneurons (LOM).
- LOM exhibited earlier onset, longer duration, and increased spike count per breath.
- Vagotomy attenuated these phrenic nerve responses.
Conclusions:
- Phrenic motoneuron activity is modulated by pulmonary mechanics via vagal reflexes.
- Late-onset motoneurons play a significant role in adapting breathing during bronchoconstriction.