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Effect of blocking medial area of nucleus retrofacialis on respiratory rhythm
1Department of Physiology, First Medical College of PLA, Guangzhou, P.R. China.
Abstract:
Experiments were performed on anaesthetized, vagotomized rabbits. Respiratory movement and phrenic rhythmical discharge were reversibly abolished by the symmetrical injection of 1% procaine into the medial area of the nucleus retrofacialis (mNRF). Blocking other areas of the medulla had no obvious effect on respiratory rhythm, with the exception of the rostral portion of the ventral respiratory group (VRG), which overlaps with the mNRF. When the mNRF was blocked, most inspiratory and expiratory neurons recorded in the VRG and DRG (dorsal respiratory group) gradually started to fire continuously, and no longer exhibited respiratory rhythm. A minority of respiratory neurons was inactivated during apnea. Stimulation of the caudal portion of the DRG and VRG evoked only a short cluster of phrenic discharges instead of rhythmical firing, indicating that the respiratory neurons situated in these areas cannot generate rhythmic activity by themselves. This suggests that the mNRF plays an important role in the genesis and maintenance of basic respiratory rhythm.
Insights
The medial nucleus retrofacialis (mNRF) is crucial for maintaining respiratory rhythm in rabbits. Blocking this area disrupts normal breathing patterns, highlighting its role in respiratory control.
Area of Science:
- Neuroscience
- Respiratory Physiology
Background:
- The neural control of breathing is complex, involving multiple brainstem nuclei.
- The precise mechanisms generating respiratory rhythm remain under investigation.
Purpose of the Study:
- To investigate the role of the medial nucleus retrofacialis (mNRF) in the genesis and maintenance of respiratory rhythm.
Main Methods:
- Experiments were conducted on anesthetized, vagotomized rabbits.
- Procaine was injected into the mNRF to reversibly block neural activity.
- Respiratory movements and phrenic nerve activity were monitored.
- Neuronal activity in the ventral (VRG) and dorsal (DRG) respiratory groups was recorded.
Main Results:
- Symmetrical blockade of the mNRF abolished respiratory movement and phrenic rhythmical discharge.
- Blocking the mNRF caused most inspiratory and expiratory neurons in the VRG and DRG to fire continuously, losing their rhythm.
- Stimulation of caudal VRG and DRG evoked only short bursts of phrenic discharges, not rhythmic firing.
Conclusions:
- The mNRF plays a critical role in generating and sustaining the basic respiratory rhythm.
- Respiratory neurons in the VRG and DRG appear to rely on input from the mNRF for rhythmic activity.