PSA-NCAM: an important regulator of hippocampal plasticity

The Neural Cell Adhesion Molecule (NCAM) serves as a temporally and spatial ly regulated modulator of a variety of cell-cell interactions. This review summarizes recent results of studies aimed at understanding its regulation of expression and biological function, thereby focussing on its polysialyla ted isoforms (PSA-NCAM). The detailed analysis of the expression of PSA and NCAM in the hippocampal mossy fiber system and the morphological consequen ces of PSA-NCAM deficiency in mice support the notion that the levels of ex pression of NCAM are important not only for the regulation and maintenance of structural changes, such as migration, axonal growth and fasciculation, but also for activity-induced plasticity. There is evidence that PSA NCAM c an specifically contribute to a presynaptic form of plasticity, namely long -term potentiation at hippocampal mossy fiber synapses. This is consistent with previous observations that NCAM-deficient mice show deficits in spatia l learning and exploratory behavior. Furthermore, our data points to an imp ortant role of the hypothalamic-pituitary-adrenal axis, which is the princi ple adaptive response of the organism to environmental challenges, in the c ontrol of PSA NCAM expression in the hippocampal formation. In particular, we evidence an inhibitory influence of corticosterone on PSA-NCAM expressio n. (C) 2000 Published by Elsevier Science Ltd on behalf of ISDN. All rights reserved.