Basic NeuroscienceThe functional and morphological characteristics of sciatic nerve degeneration and regeneration after crush injury in rats

- Ex vivo electrophysiology allows the analysis of early functional recovery after nerve crush.
- Functional recovery of nerve conduction observed over crush as early as 48 h post injury.
- Ex vivo electrophysiology is in line with findings on the morphology of the nerve.
- Each method to analyze functional recovery of the nerve after injury should be used in their own time frame.
- Functional data are essential for proper interpretations of morphological data.

BackgroundPeripheral nerve damage induces a sequence of degeneration and regeneration events with a specific time course that leads to (partial) functional recovery. Quantitative electrophysiological analysis of degeneration and recovery over time is essential to understand the process.New methodThe presented ex vivo neurophysiological method evaluates functional recovery of the propagation of the compound action potential after crush injury of the rat sciatic nerve. A 32 channel electrode array was used to monitor compound action potential propagation at time points between 1 h and 35 days after semi-quantitative crush injury of the rat sciatic nerve.ResultsThe compound action potential was characterized by four measures: the latency, the duration, the amplitude and a measure that combined time and location. These four parameters reflected the subsequent steps in early axonal degradation, the transition to rapid degeneration followed by sprouting and the long period of remyelination that accompanied regeneration.Comparison with existing methodsThe neurophysiology measures of the compound action potential were compared with the morphology of the nerve at representative time points and analysis of functional recovery of action potential propagation was compared with a behavioral test: the foot flick test.ConclusionsOur data suggests that the ex vivo electrophysiological method is complementary to the classical behavioral foot flick test in that it allows a detailed time analysis of the degeneration and early regeneration phases at a high spatial and temporal sensitivity. The results were well-matched with observations made with immunohistochemical and morphological methods.