Spinal cord transection--no loss of distal ventral horn neurons. Modern stereological techniques reveal no transneuronal changes in the ventral horns of the mouse lumbar spinal cord after thoracic cord transection.

Anterograde transneuronal degeneration is caused by the loss of afferent input to the nerve cells and may occur in a number of neuronal systems. Transection of the adult spinal cord, causing anterograde transneuronal degeneration in ventral horn neurons, distal to the lesion, has been reported by some authors, while others contend that no such changes take place. The present study was undertaken in order to investigate whether transection of adult mouse thoracic spinal cord induces neuronal death in the ventral horns distal to the lesion. By means of modern stereological techniques such as the optical dissector, the total number of cells in the lumbar ventral horns was estimated 7 weeks after transection. The mean numbers of neurons and glial and endothelial cells were 82,000 versus 89,000, 259,000 versus 301,000, and 129,000 versus 144,000 in the transected (n = 6) and sham-operated animals (n = 5), respectively. These differences were not statistically significant. Furthermore, neuronal soma volume was estimated by another stereological method, the vertical rotator. Mean neuronal soma volume was not significantly different between transected (2762 microns 3) and sham-operated (2617 microns 3) mice. Although no reduction in cell number or neuronal soma volume was observed, the mean volume of the ventral horns in the lumbar segments was significantly less in transected than in sham-operated animals, 2.49 mm3 versus 3.05 mm3 (P < 0.05). In conclusion, the transection of adult mouse thoracic spinal cord does not induce neuronal degeneration in the lumbar ventral horns.