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Effects of reversible spinalization on individual spinal neurons
Pavel V Zelenin1, Vladimir F Lyalka, Li-Ju Hsu
1Department of Neuroscience, Karolinska Institute, SE-17177, Stockholm, Sweden.
Summary
Spinalization dramatically reduces postural limb reflexes (PLRs) by altering spinal interneuron activity. This study identifies specific interneurons crucial for PLR generation and their altered function after spinalization.
Area of Science:
- Neuroscience
- Motor Control
- Spinal Cord Physiology
Background:
- Postural limb reflexes (PLRs) are vital for maintaining trunk stability in quadrupeds.
- Surgical spinalization induces spinal shock, characterized by reduced extensor tone and suppressed spinal reflexes like PLRs.
Purpose of the Study:
- To investigate changes in spinal interneuron activity, particularly those involved in PLRs, following spinalization.
- To identify interneurons responsible for the reduction of extensor tone and PLRs during spinal shock.
Main Methods:
- Recorded activity of individual L5 spinal interneurons in decerebrate rabbits during PLR stimulation.
- Utilized reversible spinalization (RS) via a cold block at T12 to temporarily abolish supraspinal influences.
- Compared interneuron activity with and without supraspinal input.
Main Results:
- 84% of recorded interneurons (n=199) showed activity correlated with PLRs.
- Reversible spinalization significantly reduced PLRs, mimicking surgical spinalization effects.
- RS decreased mean firing frequency in 67% of interneurons, increased it in 15%, and had no effect on 18%.
- Interneurons showing decreased activity during RS were predominantly located in the intermediate and ventral spinal cord areas.
Conclusions:
- A significant population of spinal interneurons contributes to the generation of PLRs.
- Specific interneurons, coactivated with extensors during PLRs, exhibit marked activity reduction during RS, implicating them in the loss of extensor tone during spinal shock.
