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) activation in controlling polysialylated neural cell adhesion molecule (PSA-NCAM) dynamic expression in the dorsal vagal complex (DVC), a gateway for many primary afferent fibres. In this structure the overall expression of PSA-NCAM decreases during the first 2 weeks after birth to persist only at synapses in the adult. Electrical stimulation of the vagal afferents causes a rapid increase of PSA-NCAM expression both in vivo and in acute slices before postnatal 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 all stages. By contrast, blockade of neuronal nitric oxide synthase (nNOS) prevented 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.