Co-activation of synaptic and extrasynaptic NMDA receptors by neuronal insults determines cell death in acute brain slice.

Overactivation of NMDA receptors is linked to cell death during neuronal insults. However the precise role of synaptic and extrasynaptic NMDA receptors remains to be further determined. In this study, we used the acute brain slice to examine the contributions of synaptic and extrasynaptic NMDA receptors to neuronal death. By activation of synaptic NMDA receptors with bath application of 100 µM bicuculline in acute brain slices, we observed a significant up-regulation in activation of neuronal survival-related signaling (p-CREB, p-ERK1/2 and p-AKT), without an obvious increase of LDH release and neuronal death. Interestingly, activation of extrasynaptic NMDA receptors alone by high dose of glutamate (200 µM) following blockade of synaptic NMDA receptors with co-application of 20 µM MK801 and 100 µM bicuculline, we failed to observe inhibition of neuronal survival signaling and neuronal damage. In contrast, co-activation of synaptic and extrasynaptic NMDA receptors by applying 200 µM glutamate or oxygen-glucose deprivation (OGD) to acute brain slices for 30 min, we observed a significant inhibition of CREB, ERK1/2 and AKT activation, an increase of LDH release and neuronal condensation. Together, co-activation of synaptic and extrasynaptic NMDA receptors by neuronal insults contributes to cell death in acute brain slice.