The effect of neonatal peripheral nerve section on the somadendritic growth of sensory projection cells in the rat spinal cord

Sciatic nerve section and ligation on the day of birth results in marked growth retardation of the rat dorsal horn. This transneuronal effect was examined in spinal cord cells that project to the brain by retrograde labelling with HRP from contralateral dorso- and ventrolateral tracts in the thoracic white matter. HRP-impregnated gel pellets were implanted in the tracts for 48-72 h to allow intense somadendritic staining of the projection cells. The results show that cells in rats whose sciatic nerve has been sectioned at birth have a mean somal area that is 40% smaller than controls. Primary dendrites are reduced from a mean of 4.1 per cell to 3.1 per cell and secondary branching is reduced by 75%. The results suggest that there was no actual cell death, only growth retardation. An intact primary afferent input apparently has a strong transneuronal trophic influence on spinal cord sensory cells projecting to the brain.