Abstract: To observe the changes of the cell body and nucleolus of neurons in the dorsal root ganglion of rabbits with different ages after an injure in the peripheral processes of those neurons, the brachial plexus were transected unilaterally in 12 rabbits in ages with 0, 1, 2, 3, 4 and 8 weeks, respectively. The cell numbers were counted and the sizes of cell bodies and nucleoli were measured bilaterally in the dorsal root ganglia from the segments of C₄～T₂ after 3 months of the operation. The nucleolus was selected as the counted unit and counted number was corrected according to K.. onigsmark's formula. The measurements of cell bodies and nucleoli were done with a device of image analyzer and 1 200 neurons were randomly selected to be measured. The results showed that the cell number of dorsal root ganglia from the lesion side of C₄～T₂ was markedly decreased compared with normal side after transecting of the plexus. The neurons with small or medium size were decreased even more distinctly among those decreased neurons. In addition, the cell loss was more seriously in younger animals than that in those older ones.

Key words: dorsal root ganglia, neuronal number, brachial plexus transaction