Cellular neuroscienceFacilitated sprouting in a peripheral nerve injury
Section snippets
Animals
The experiments used male Sprague–Dawley rats of initial weight 200–330 g maintained in cages with shavings covered plastic flooring and exposed to normal day-light cycles. Procedures were carried out under pentobarbital anesthesia (65 mg/kg) and postoperative meperidine or butorphanol were provided for analgesia. The number of rats used was minimized and their suffering minimized using appropriate anesthesia and analgesia. All procedures were reviewed an approved by the University of Calgary
Heightened axon outgrowth
We studied longitudinal sections of nerves, taken through the crush zone and labeled with an antibody directed against a Nf subunit (Nf200). These sections were taken at an early time point, 7 days after injury, to address whether enhanced sprouting occurred soon after the onset of regrowth. In our experience, a 7 day time point after crush is optimal for identifying new axons that express Nf and that can be distinguished from breakdown Nf products during Wallerian-like degeneration. At
Overall findings
In this work, we describe an interesting, unexpected and novel response of regenerating peripheral nerve axons to their microenvironment. Injuries with a simple alteration in the extent of direct injury had dramatically different impacts on axon behavior. We believe that longer segmental crush injuries may actually be more common in complex human traumatic injuries than narrow circumscribed “surgical” focal crushes traditionally applied by experimentalists. Both injuries are classified as type
Conclusion
In summary, we have identified a form of facilitated axon sprouting and maintenance associated with a simple alteration in the microenvironment of an injured peripheral nerve. Understanding the signals for this phenomenon may allow it to be exploited when this kind of plasticity is desirable during regeneration.
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