Morphological alterations in dorsal root ganglion neurons after peripheral axon injury: association with changes in metabolism.

Axotomized rat sensory ganglion neurons have been shown to undergo rapid metabolic changes in the first 2 weeks after injury. The present study examined selected morphological features of these neurons over the same time period. Parameters studied included the position of the cell nucleus (eccentricity) and soma, nuclear, and nucleolar size over time periods primarily in the first 2 weeks after a unilateral crush injury of the sciatic nerve. Comparisons were made with normal ganglia and ganglia contralateral to the injury. The eccentricity of the nucleus in injured neurons was significantly altered within 1 day after injury and remained so over the entire time period studied. Alterations in neuron soma included an initial decrease in size at 1 day followed by a significant bilateral increase at 3 days after injury. Nuclear and nucleolar size changes were phasic with significant increases size peaking at 3-4 and 8-11 days after injury. These alterations coincided temporally with known changes in RNA synthesis occurring in these neurons after injury. Significant alterations in all parameters were observed on the uninjured side. Preliminary studies of the bilateral changes suggested that the trauma of the operation may be the major factor in this response. The data suggest that significant morphological alterations parallel the rapidly fluctuating change in neuronal metabolism after axon injury.