Polysialylation as a regulator of neural plasticity in rodent learning and aging.

Although generally accepted to play an important role in development, the precise functional significance of NCAM remains to be elucidated. Correlative and interventive studies suggest a role for polysialylated NCAM in neurite elaboration. In the adult NCAM polysialylation continues to be expressed in regions of the central nervous system which retain neuroplastic potential. During memory formation modulation of polysialylation on the synapse-enriched isoform of NCAM occurs in the hippocampus. The polysialylated neurons of this structure have been located at the border of the granule cell layer and hilar region of the dentate and their number increases dramatically during memory consolidation. The converse is also true for a profound decline in the basal number of polysialylated neurons occurs with ageing when neural plasticity becomes attenuated. In conclusion, it is suggested that NCAM polysialylation regulates ultrastructural plasticity associated with synaptic elaboration.