Dorsal rhizotomy induces transient expression of the highly sialylated isoform of the neural cell adhesion molecule in neurons and astrocytes of the adult rat spinal cord.

Expression of the weakly adhesive, highly sialylated isoform of the neural cell adhesion molecule is a feature common to cell capable of migration and conformation changes. 11,18,19 Polysialylated neural cell adhesion molecule also intervenes in axonal outgrowth and synaptogenesis during development and after lesion. 11,13 High levels of polysialylated neural cell adhesion molecule immunoreactivity are normally visible in laminae I,II and X of the adult rat spinal cord. 2,15 We how here that unilateral cervical dorsal rhizotomy induced no detectable changes in immunoreactivity in these areas. However, 24 h after lesion, polysialylated neural cell adhesion molecule immunoreactivity appeared in neurons scattered in laminae III-IX, ipsi-and contralateral to lesion. This reaction increased particularly on the contralateral side, became maximal at four days and disappeared eight days later. At this time, there was immunolabelling of astrocytes with an activated morphology. The astrocytic labelling, predominant on the side ipsilateral to the lesion, was strongest 12 days after rhizotomy, then diminished progressively. Deafferentation thus causes a transient expression of polysialylated neural cell adhesion molecule within areas of the spinal cord distinct from those which permanently express this adhesion molecule. Such expression occurs both in neurons and glial cells, with a temporal pattern specific to each type of cell.