Dual effects of NMDA receptor activation on polysialylated neural cell adhesion molecule expression during brainstem postnatal development

Here we show a dual role of N-methyl-D-aspartate receptor (NMDAR) activatio n in controlling polysialylated neural cell adhesion molecule (PSA-NCAM) dy namic expression in the dorsal vagal complex (DVC), a gateway for many prim ary afferent fibres. In this structure the overall expression of PSA-NCAM d ecreases during the first 2 weeks after birth to persist only at synapses i n the adult. Electrical stimulation of the vagal afferents causes a rapid i ncrease of PSA-NCAM expression both in vivo and in acute slices before post natal day (P) 14 whereas a similar stimulation induces a decrease after P15 . Inhibition of NMDAR activity in vitro completely prevented these changes. These regulations depend on calmodulin activation and cGMP production at a ll stages. By contrast, blockade of neuronal nitric oxide synthase (nNOS) p revented these changes only after P10 in agreement with its late expression in the DVC. The pivotal role of NMDAR is also supported by the observation that chronic blockade induces a dramatic decrease in PSA-NCAM expression.