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

BACKGROUND: Peripheral 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 METHOD: The 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 1h and 35 days after semi-quantitative crush injury of the rat sciatic nerve. RESULTS: The 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 METHODS: The 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.
CONCLUSIONS: Our 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.