Sciatic Nerve Transection-Induced Morphological Changes in the Dorsal Root Ganglia of Rabbits: A Light Microscopic Study

The dorsal root ganglion (DRG) is the gateway for almost all modalities of sensory inputs to the brain but the etiology of various pain syndromes induced by peripheral nerve injury remains unresolved. The present study was carried on 24 healthy adult rabbit of either sex divided into four groups having 6 rabbits each. Under general anesthesia right sciatic nerve of all experimental animals were transected. After different post-lesional intervals (2d, 1w, 1m, 3m) rabbits were sacrificed and perfusion fixed by 10% formalin. Lumbosacral DRG from both sides were processed for paraffin embedding. Light microscopic observation on Haematoxyllin and Eosin stained sections from control (Left side) showed clusters of DRG neurons of different sizes interspersed among the fascicles of nerve fibers. They had round somata filled with Nissl substance and centrally placed euchromatic nuclei. Each neuron was surrounded by 3 – 15 satellite glial cells (SGCs). In the experimental group (Right side) the DRG neurons quite often showed eccentrically placed nucleus in association with de-granulation of Nissl substance. Most of the affected neurons were of large and medium size. The adjoining areas of degenerating neurons were also attended with degeneration of nerve fascicle, and also showed an apparent increase in the number of satellite glial cells. Interestingly, these changes were also noticed in the contralateral (left side) lumbosacral DRG as well though they were of much lower intensity. It is concluded that unilateral spinal nerve transection induces bilateral degeneration of neurons and nerve fibres and glial cell proliferation. These changes are marked ipsilaterally and their severity is not strictly time-dependent.