期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2010
卷号：107
期号：34
页码：15252-15257
DOI：10.1073/pnas.0906551107
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：The GluN2B (GluR{varepsilon}2/NR2B) and GluN2A (GluR{varepsilon}1/NR2A) NMDA receptor (NMDAR) subtypes have been differentially implicated in activity-dependent synaptic plasticity. However, little is known about the respective contributions made by these two subtypes to developmental plasticity, in part because studies of GluN2B KO [Grin2b-/- (2b-/-)] mice are hampered by early neonatal mortality. We previously used in vitro slice cocultures of rodent cerebral cortex (Cx) and spinal cord (SpC) to show that corticospinal (CS) synapses, once present throughout the SpC, are eliminated from the ventral side during development in an NMDAR-dependent manner. To study subtype specificity of NMDAR in this developmental plasticity, we cocultured Cx and SpC slices derived from postnatal day 0 (P0) animals with different genotypes [2b-/-, Grin2a-/- (2a-/-), or WT mice]. The distribution of CS synapses was studied electrophysiologically and with a voltage-sensitive dye. Synapse elimination on the ventral side was blocked in WT(Cx)-2b-/-(SpC) pairs but not in WT(Cx)-2a-/-(SpC) or 2b-/-(Cx)-WT(SpC) pairs. CS axonal regression was also observed through live imaging of CS axons labeled with enhanced yellow fluorescent protein (EYFP) through exo utero electroporation. These findings suggest that postsynaptic GluN2B is selectively involved in CS synapse elimination. In addition, the elimination was not blocked in 2a-/- SpC slices, where Ca2+ entry through GluN2B-mediated CS synaptic currents was reduced to the same level as in 2b-/- slices, suggesting that the differential effect of GluN2B and GluN2A in CS synapse elimination might not be explained based solely on greater Ca2+ entry through GluN2B-containing channels.
