Temperature can alter the functional outcome of spinal cord regeneration in larval lampreys
Section snippets
Lesion
Under anesthetic (tricaine methane sulfonate, MS222), a dorsal incision was made just rostral to the dorsal fin of larval lampreys, Ichthyomyzon unicuspis. The spinal cord was exposed, and a no. 5 forceps slipped above and below the spinal cord at about segment 25. The forceps were compressed fully for 30 or more seconds. Since the spinal cord is so thin (no more than 250 μm), the delicate forceps are more than satisfactory for this procedure, and they do less damage than a larger instrument
Results
The results summarized below include only those animals for which all tests of function could be fully completed. Partial testing and observations on an additional 14 animals in the cold and four at room temperature were consistent with the results described below, but were not included in the summary tables. They are discussed only as relevant.
Discussion
We present here evidence that the lamprey can serve not only as a model for successful spinal regeneration, but also as a model for dysfunctional recovery. The data presented demonstrate that the functional outcome of spinal cord regeneration can be drastically altered with only a slight change in the conditions under which an animal recovers. Holding other conditions constant, lampreys which recover at room temperature (20–22°C) are apt to exhibit only normal motor patterns during whole animal
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Acknowledgements
This work was supported by NIH grant NS16803 and a grant from the American Paralysis Association to A.H.C.
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2011, NeuroscienceCitation Excerpt :However, while the sensory and excitability changes in isolation did not correlate with the degree of recovery, there were differences in how across-lesion responses interacted with rostral excitability changes in animals that recovered well or poorly. This interaction could contribute to the variable association between the magnitude of across-lesion responses and recovery, and may also account for the lack of sufficiency of regenerated inputs in recovery (e.g. see Cohen et al., 1989, 1999; McClellan, 1990; Selzer, 1978). The nature of the interaction is currently unknown: positive correlations between across-lesion stimulation responses and sublesion excitability changes could simply reflect the stimulation of larger numbers of regenerated axons, but this cannot account for the negative correlations associated with poor recovery.
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Present address: University of Maryland Medical School, Baltimore, Maryland, U.S.A.