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Central inspiratory influence on abdominal expiratory nerve activity
1Department of Physiology, Dartmouth Medical School, Hanover, New Hampshire 03756.
Journal of Applied Physiology (Bethesda, Md. : 1985)
|October 1, 1988
Summary
The intensity of abdominal expiratory nerve activity is influenced by preceding inspiratory phrenic nerve activity. This study in cats reveals a strong link between phrenic nerve discharge and subsequent abdominal muscle activation during breathing.
Area of Science:
- Neuroscience
- Respiratory Physiology
Background:
- The neural control of breathing involves complex interactions between inspiratory and expiratory phases.
- Understanding the afferent influences on respiratory motor output is crucial for respiratory control research.
Purpose of the Study:
- To investigate if inspiratory phrenic nerve discharge intensity conditions abdominal expiratory nerve discharge intensity.
- To determine this relationship independent of mechanical and chemical afferent feedback.
Main Methods:
- Experiments were conducted on decerebrate, paralyzed, vagotomized cats under hyperoxic normocapnia with bilateral pneumothoraxes.
- Phrenic and abdominal (L1) nerve activities were recorded.
- Inspiration was prematurely terminated or altered using superior laryngeal nerve (SLN) or vagal nerve stimulation.
Main Results:
- Premature termination of inspiration reduced expiratory duration and abdominal nerve activity, with a greater reduction in abdominal activity (51%) than expiratory duration (14%).
- Similar results were observed with vagal nerve stimulation and spontaneous premature inspiration terminations.
- Stimulation during expiration increased abdominal expiratory nerve activity, suggesting a gating mechanism.
Conclusions:
- Inspiratory phrenic nerve discharge intensity significantly influences subsequent abdominal expiratory nerve activity.
- A gating mechanism during inspiration may allow for the expression of this inspiratory conditioning effect on expiration.