Sciatic nerve transection in neonatal rats induces apoptotic neuronal death in L5 dorsal root ganglion

Transection of a peripheral nerve in neonatal rats induces death of the axo tomized neurons which may be due to either necrosis or apoptosis. In the pr esent investigation, neuronal cell death in L5 dorsal root ganglion was eva luated after unilateral sciatic nerve transection in rats at 1, 3, 5, 7 and 10 days age. After 5 days, right (experimental) and left (control) dorsal root ganglia in all groups were removed, fixed, processed and embedded for either light or electron microscopy. Normal nucleoli were counted in paraff in embedded serial sections, and correction factors for split and multiple nucleoli were applied as well as the physical disector. The number of neuro ns in the right dorsal root ganglia, as compared with the controls, was sig nificantly lower in all groups, and the percentage of the reduction at 1, 3 , 5, 7 and 10 days was 32.4, 27.2, 23.8, 22.8 and 21.8% respectively. On th e other hand, the results of neuronal counts using the disector method show ed 34.0, 25.7, 20.2, 20.0 and 14.2% reduction in the number of neurons at 1 , 3, 5, 7 and 10 days, respectively. The microscopic and ultrastructural re sults indicated that there were typical morphological changes similar to th ose of apoptosis, including condensed basophilic nuclei, formation of nucle ar caps, cell shrinkage and apoptotic body formation. We concluded that the re is an increase in apoptosis in dorsal root ganglia following sciatic ner ve axotomy with the greatest neuronal loss on postnatal day 1.