The influence of regeneration and nerve growth factor on the neuronal cell body reaction to injury

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Abstract
The consequence of neuronal regeneration on the affected cell body has not been well documented previously. The long-term effects of either successful peripheral nerve (sciatic) regeneration or exogenously administered nerve growth factor (NGF) on dorsal root ganglion (DRG) neurons were determined. The degree of neuronal death and changes in neuronal size were measured after various injuries and treatments. The regenerative influence of the transected, distal sciatic-nerve segment on the neuronal cell body was examined under various standardized conditions (e.g. crush, transection followed by immediate epineurial anastomosis or transection with capping of the proximal nerve stump). Neuronal death was greatest in smaller neurons with diameters between 16 and 28 μm. The data showed no difference in the degree of neuronal death between the crush injury and the anastomosis (both able to regenerate). However, the capped, proximal nerve (regeneration prevented) had a significantly higher incidence of neuronal death and less complete recovery from the early neuronal atrophy, which was initially observed in all three groups. The long-term effect on neuronal survival of transient NGF administration (three weeks) at the site of injury demonstrated partial protection by a decrease (55%) in the neuronal loss nine weeks after injury compared to controls. Either the distal nerve segment during regeneration or exogenously applied NGF is capable of mitigating the long-term effects of axotomy in the DRG neuronal cell body.