Routine hypercapnic challenge after cervical spinal hemisection affects the size of phrenic motoneurons

Scientific Reports, 2023 · DOI: 10.1038/s41598-023-40505-x · Published: August 11, 2023

Simple Explanation

After a cervical cord injury, the diaphragm and external intercostal muscles can become paralyzed, leading to reduced lung capacity and difficulty with deep inspiration, increasing the risk of respiratory complications. Respiratory muscle training is used in early rehabilitation to help patients recover respiratory function and prevent these complications. This study investigates whether a routine hypercapnic challenge (exposure to high CO2) can alter the adaptation of phrenic motoneurons (nerve cells that control the diaphragm) after a cervical spinal cord injury in rats.

Study Duration

3 weeks

Participants

17 male Wistar rats

Evidence Level

Not specified

Key Findings

1
The average diameter, cross-sectional area, and somal surface area of stained phrenic motoneurons were significantly smaller in the control group compared to the other groups.
2
A routine hypercapnic challenge after C2HS may affect the adaptations of phrenic motoneurons.
3
High CO2 may have increased the rats’ descending inspiratory excitatory drive, since high CO2 was reported to increase phrenic nerve activity in addition to ventilation parameters.

Research Summary

This study examined the morphological differences in phrenic motoneurons between control rats that underwent a C2HS, rats that underwent both a C2HS and a 3-week hypercapnic challenge, rats that underwent only a sham operation, and rats that underwent both the sham operation and the 3-week hypercapnic challenge. The C2HS rats exposed to high CO2 showed increased ventilation parameters. The rats that underwent an early post-C2HS hypercapnic challenge for 3 weeks did not exhibit smaller phrenic motoneuron sizes compared to the rats that did not undergo this intervention.

Practical Implications

Rehabilitation Strategies

The findings suggest that early hypercapnic challenge post-spinal cord injury may help maintain phrenic motoneuron size, potentially improving respiratory function recovery.

Clinical Translation

The limited number of hypercapnic sessions needed to induce morphological changes suggests the potential for practical application in rehabilitation settings.

Further Research

Future studies should investigate the functional aspects of these morphological changes and explore the underlying mechanisms of motoneuron adaptation.

Study Limitations

1
The study analyzed only morphological characteristics and did not measure functional aspects.
2
Not all HRP-labeled motoneurons could be observed due to overlap or incomplete cell bodies.
3
The mechanism underlying the motoneurons’ adaptations resulting from the routine hypercapnic challenge after cervical cord injury are not clear from the present results.

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