Studies on the phrenic nerve and diaphragmatic plexus in rabbits and gerbils

Thorax, 1972 · DOI: · Published: January 1, 1972

Simple Explanation

This research explores the nerve fibers in the phrenic nerve and diaphragmatic plexus of gerbils, small desert rodents. The study involved surgically cutting the phrenic nerve in the chest to observe changes in the diaphragmatic plexus, phrenic nerve, and phrenic nucleus. The phrenic nucleus in gerbils, responsible for controlling the diaphragm, extends from the second to the sixth cervical segment, which is more extensive than in other species. This configuration might relate to the diaphragm's dual function, both voluntary and involuntary. The study also examined the effects of cutting the phrenic nerve and found persisting nerve fibers within the diaphragm, suggesting a potential crossover of nerve fibers or an additional nerve supply to the diaphragm.

Study Duration

2 to 196 days

Participants

Rabbits and Gerbils

Evidence Level

Not specified

Key Findings

1
The phrenic nucleus in gerbils is more extensive than in other species, spanning from the second to the sixth cervical segment of the spinal cord.
2
Even after the phrenic nerve is cut, some nerve fibers persist within the diaphragm, indicating potential crossover or an alternative nerve supply.
3
The myelinated fibers in the gerbil's phrenic nerve show little change in numbers at different levels, suggesting possible intraneural branching to maintain a steady level.

Research Summary

The study investigates the phrenic nerve and diaphragmatic plexus in gerbils, focusing on nerve fiber distribution, spinal cord connections, and structural features. It also compares findings with those from rabbits. Experiments involved surgical transection of the phrenic nerve to observe changes in the phrenic nucleus and nerve fibers. The researchers used histological methods, including silver and gold impregnation, to visualize nerve structures. Key findings include the extensive phrenic nucleus in gerbils, the persistence of nerve fibers after transection, and the presence of muscle spindles in the diaphragm. These observations contribute to understanding diaphragmatic innervation and its control.

Practical Implications

Comparative Neuroanatomy

Highlights species-specific differences in phrenic nerve anatomy, particularly the extent of the phrenic nucleus, necessitating species-specific considerations in research.

Respiratory Control Mechanisms

Suggests the presence of alternate pathways for diaphragmatic innervation, which may have implications for understanding respiratory control and compensatory mechanisms after nerve injury.

Clinical Relevance

The diffuse nature of the phrenic nucleus and potential for nerve fiber crossover may influence the effectiveness of interventions targeting the phrenic nerve, such as phrenic nerve stimulation.

Study Limitations

1
Small sample sizes for some experiments (e.g., topographical studies with only three gerbils).
2
The study primarily focuses on gerbils and rabbits, limiting the generalizability of findings to other species.
3
The precise origin of regenerating nerve fibers after phrenic nerve transection was not definitively located.

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