THE EFFECT OF INCREASING THE INNERVATION FIELD SIZES OF NERVES ON THEIR REFLEX RESPONSE TIME IN SALAMANDERS

J. Physiol., 1973 · DOI: · Published: January 1, 1973

Physiology Neurology Regenerative Medicine & Stem Cells

Simple Explanation

This study investigates how the size of a nerve's connection area (innervation field) affects reflex speed in salamanders. Researchers measured how quickly reflexes occurred when stimulating and recording from different nerve pairs in the hind limbs. When a nerve was cut, the neighboring nerves sprouted to cover the lost area. The experiment found that reflexes became faster between nerves that had enlarged their innervation fields due to this sprouting. The findings suggest the salamander spinal cord can adapt to changes in nerve connections, making reflexes more efficient when nerves expand their reach. This shows a functional adaptation in the spinal cord.

Study Duration

Not specified

Participants

Adult European salamanders (Salamandra 8alamandra)

Evidence Level

Not specified

Key Findings

1
Reflex response times (S/R times) were shorter when the stimulated nerve had a larger innervation field, especially between the 15th and 17th segmental nerves.
2
After cutting or crushing the 16th nerve, adjacent nerves sprouted collaterally to innervate the denervated area, leading to complete recovery of tactile reflexes and walking movements within a month.
3
When nerves increased their innervation field size, the S/R times between them were significantly shorter on the operated side when the nerve with the enlarged field was stimulated.

Research Summary

The study aimed to quantify the relationship between reflex coupling in the spinal cord and the peripheral innervation fields of nerves in salamanders. Experiments involved recording reflex responses between cut hind limb nerves in decerebrate salamanders and observing the effects of nerve regeneration after surgical interventions. Results indicated that reflex response times decreased when nerves increased their innervation field sizes, suggesting an adaptive capacity in the spinal cord.

Practical Implications

Spinal Cord Plasticity

Demonstrates the adult spinal cord's ability to adapt and reorganize neural circuits in response to peripheral nerve damage and subsequent regeneration.

Reflex Efficiency

Highlights the functional significance of innervation field size in determining reflex response times, suggesting that larger fields result in more efficient reflex pathways.

Rehabilitation Potential

Suggests potential targets for therapeutic interventions aimed at promoting nerve regeneration and functional recovery after nerve injuries.

Study Limitations

1
The study did not record reflexes before and after peripheral field changes in the same animal, relying on the unoperated side as a control.
2
The exact mechanisms underlying the shortening of reflex response times were not fully elucidated.
3
The study was conducted on salamanders, and the findings may not be directly applicable to other species.

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