Looking After Polysialic Acid

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Science  14 Dec 2007:
Vol. 318, Issue 5857, pp. 1699
DOI: 10.1126/science.318.5857.1699c

In some cases, the effects of neuronal activity are restricted to particular developmental stages. For instance, the loss of visual input from one eye early in life leads to a shift in the responsiveness of neurons in the visual cortex toward the functional eye. The onset and time course of this critical period for ocular dominance plasticity are influenced by the maturation of GABAergic innervation, which is itself regulated by visual input and neuronal activity. Di Cristo et al. found that polysialic acid [PSA, a homopolymer of sialic acid that attaches to neural cell adhesion molecule (NCAM) and modulates intercellular bonds] and NCAM were abundant in the neonatal mouse visual cortex but that PSA underwent a steep decline after eye opening. Pups reared in the dark showed increased PSA as compared with pups reared under conventional light/dark cycles. Injection of endoneuramidase (which cleaves off PSA) into the visual cortex promoted both perisomatic GABAergic innervation and the frequency of miniature inhibitory postsynaptic currents. Moreover, it stimulated the early onset of the critical period for ocular dominance plasticity. Thus, maturation of GABAergic inhibition—and thereby the initiation of ocular dominance plasticity—is regulated by an activity-dependent decrease in PSA. — EMA

Nat. Neurosci. 10, 1569 (2007).

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