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Synchronization of respiratory frequency by somatic afferent stimulation
Journal of Applied Physiology
|February 1, 1976
Summary
Stimulating nerves in cats can alter breathing patterns, sometimes locking respiratory rate to the stimulation rhythm. This reveals a reflex mechanism linking somatic input to breathing, relevant to exercise physiology in humans.
Area of Science:
- Neuroscience
- Respiratory Physiology
- Exercise Physiology
Background:
- The relationship between somatic afferent input and respiratory control is complex.
- Understanding how external rhythms influence breathing is crucial for exercise science.
Purpose of the Study:
- To investigate the effects of somatic afferent nerve stimulation on respiratory patterns in anesthetized cats.
- To explore the potential for respiratory frequency entrainment by periodic somatic input.
Main Methods:
- Stimulation of superficial radial (cutaneous) and hamstring (muscle) nerve afferents in vagotomized, paralyzed, and artificially ventilated cats.
- Recording of phrenic nerve electrical activity to assess respiratory motoneuron output.
- Analysis of changes in respiratory timing, phrenic motoneuron firing patterns, and respiratory frequency.
Main Results:
- Nerve stimulation altered the timing of inspiration and expiration, affecting their duration.
- Phrenic motoneuron firing patterns showed changes like earlier recruitment and increased discharge frequency.
- Repetitive stimulation led to sustained increases in respiratory frequency, with entrainment observed in 50% of cats.
- Cutaneous afferents required lower stimulus intensity for phase shifts compared to muscle afferents.
Conclusions:
- A reflex mechanism exists that can lock respiratory frequency to periodic somatic afferent input.
- These findings provide experimental support for the hypothesis that reflexes mediate the coupling of limb movement frequency to respiratory rate during human exercise.