NODAL AND TERMINAL SPROUTING FROM MOTOR NERVES IN FAST AND SLOW MUSCLES OF THE MOUSE

J. Physiol., 1980 · DOI: · Published: January 1, 1980

Simple Explanation

This study investigates how motor nerves sprout in fast and slow muscles of mice, focusing on nodal and terminal sprouting. They used a special stain to visualize the nerves. The research found that electrically stimulating paralyzed muscles can prevent the nerve terminals from sprouting. However, stimulating the muscles did not reduce sprouting from nodes in partially denervated spinal preparations. The study suggests that the stimulus for terminal sprouting comes from inactive muscle fibers, while the signal for nodal sprouting likely comes from a different source, though further research is needed.

Study Duration

Not specified

Participants

Adult white mice (Carworth CFLP, and OLAC strains) weighing 20-45 g

Evidence Level

Not specified

Key Findings

1
Electrical stimulation of paralyzed muscles prevents terminal sprouting but does not affect nodal sprouting in partly denervated spinal preparations.
2
The amount of terminal sprouting is linearly related to the degree of paralysis caused by botulinum toxin, but not to the degree of denervation in partly denervated muscles.
3
Fast muscles show relatively more nodal sprouting and less terminal sprouting compared to slow muscles after partial denervation. Full paralysis with botulinum toxin allows fast muscles to develop as much terminal sprouting as slow muscles.

Research Summary

This study investigated nodal and terminal sprouting in fast and slow muscles of the mouse hind limb using the zinc iodide and osmium tetroxide stain. Terminal sprouting elicited by botulinum toxin can be prevented by direct electrical stimulation of muscle fibers, but nodal sprouting in partly denervated spinal preparations is not reduced by such stimulation. The source of the signal for terminal sprouting is likely denervated muscle fibers, while the signal for nodal sprouting may originate from a different source, requiring further investigation.

Practical Implications

Understanding Nerve Regeneration

The findings contribute to understanding the mechanisms of nerve regeneration and sprouting in response to muscle inactivity or denervation.

Therapeutic Interventions

Electrical stimulation may be a potential therapeutic intervention to control unwanted nerve sprouting in certain conditions.

Muscle-Specific Responses

The differences in sprouting patterns between fast and slow muscles highlight the importance of considering muscle-specific responses in nerve regeneration studies.

Study Limitations

1
The study used a specific staining technique (ZIO), which may have limitations in detecting all nodal sprouts.
2
Partial muscle block with botulinum toxin may not have uniformly blocked all terminals.
3
The study focused on specific muscles in mice, and the findings may not be directly applicable to other muscles or species.

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