A ROLE FOR N-METHYL-D-ASPARTATE RECEPTORS IN THE REGULATION OF SYNAPTOGENESIS AND EXPRESSION OF THE POLYSIALYLATED FORM OF THE NEURAL CELL-ADHESION MOLECULE IN THE DEVELOPING STRIATUM

Striatal development proceeds during a protracted postnatal period in rats. In the dorsolateral striatum, the number of asymmetric synapses, formed mostly by glutamatergic afferents innervating the dendritic sp ines of medium-sized striatal neurons, increases during the 3rd postna tal week and then rapidly declines before reaching adult levels. The p olysialylated form of the neural cell adhesion molecule (PSA-NCAM), wh ich is widely expressed along neuronal membranes early in development, becomes progressively localized to synapses, and is no longer detecta ble in remaining synapses after synaptic pruning has occurred. Adminis tration of MK-801, an antagonist of N-methyl-D-aspartate receptors, on day 20, either peripherally or locally into the striatum, decreases a symmetric synapse number by 30% and totally abolishes immunolabelling for PSA-NCAM in the dorsolateral striatum.