A STUDY OF WALLERIAN DEGENERATION

Abstract

In cats, the peroneal and popliteal branches were studied 1-4 days after the sciatic nerve was cut. The electrical excitability of degenerating nerves is decreased because, although the time parameter is not significantly changed, the voltage parameter is higher than normal. The composite spike potential of the nerve trunk decreases as some of the fibers cease conducting. The spike magnitude per fiber is greater than normal at some time before conduction stops. Degeneration follows a centrifugal course[long dash]i.e., it is more marked at a given time in the central than in the peripheral end of the excised nerves. The conduction velocity first increases, then slows during degeneration. The degenerating nerves are more fatigable than the normal[long dash]i.e., for a given relatively high frequency and relatively long period of stimulation, the decline of the spike-potential and the slowing of conduction rate are greater in the degenerating nerves. The role of edema and of the early regression of the myelin sheath during degeneration is discussed. These factors play a part in but do not account for all the changes encountered. Conduction ceases suddenly; the factor responsible is unknown.