Intercostal nerve transection and its effect on the dorsal root ganglion. A quantitative study on thoracic ganglion cell numbers and sizes in the rat.

The effect of intercostal nerve transection on the number and size distribution of thoracic spinal ganglion cells has been investigated and correlated with transganglionic degeneration (TGD) in the spinal cord dorsal horn. Unilateral transections were made of 3 or 11 consecutive intercostal nerves. Twenty to 180 days later the animals were perfused and relevant ganglia from both sides embedded in resin, serially sectioned and stained. Counts of neuronal nucleoli were made and perikaryal areas of ganglion cells measured. The number of neurons was significantly reduced on the operated side 20 days postoperatively. The cell loss increased slightly to about 35% with longer survival times. Analysis of cell size spectra showed a bilaterally symmetrical picture in normal animals. No distortions of the cell size spectrum were observed at 20 to 70 days after nerve transections. Transganglionic degeneration was found in the dorsal horn from 20 to 70 days postoperative survival, but not at 180 days. The findings indicate that TGD in the dorsal horn is related to a loss of ganglion cells in the corresponding spinal ganglion. There does not seem to be a preferential loss of any particular size class of cells.