Developmental regulation of subunit composition of extrasynaptic NMDA receptors in neocortical neurones

NMDA receptors undergo drastic changes in their subunit composition during development of the mammalian neocortex. An increase in the expression of th e NR2A subunit correlates with developmental changes in the properties of s ynaptic NMDA receptors, In this study, we investigated whether these develo pmental alterations are restricted to synaptic NMDA receptors or whether si milar developmental changes also occur at extrasynaptic NMDA receptors. To analyse the properties of extrasynaptic receptors, glutamate-evoked ion cur rents mediated by extrasynaptic NMDA receptors were isolated by irreversibl y blocking synaptic NMDA receptors with MK-801. Whole-cell ion currents med iated by extrasynaptic receptors showed developmental changes in their sens itivity against the NR2B subunit-specific antagonist ifenprodil similar to that of synaptic receptors. In summary, our results strongly suggest that N R2A subunit-containing NMDA receptors increasingly contribute also to extra synaptic NMDA receptors during in vitro differentiation. NeuroReport 11:120 3-1208 (C) 2000 Lippincott Williams & Wilkins.