Involvement of synaptic NR2B-containing NMDA receptors in long-term depression induction in the young rat visual cortex in vitro.

Activation of N-methyl-D-aspartate receptors (NMDARs) has been implicated in various forms of synaptic plasticity depending on the receptor subtypes involved. However, the contribution of NR2A and NR2B subunits in the induction of long-term depression (LTD) of excitatory postsynaptic currents (EPSCs) in layer II/III pyramidal neurons of the young rat visual cortex remains unclear. The present study used whole-cell patch-clamp recordings in vitro to investigate the role of NR2A- and NR2B-containing NMDARs in the induction of LTD in visual cortical slices from 12- to 15-day old rats. We found that LTD was readily induced in layer II/III pyramidal neurons of the rat visual cortex with 10-min 1-Hz stimulation paired with postsynaptic depolarization. D-APV, a selective NMDAR antagonist, blocked the induction of LTD. Moreover, the selective NR2B-containing NMDAR antagonists (Ro 25-6981 and ifenprodil) also prevented the induction of LTD. However, Zn2+, a voltage-independent NR2A-containing NMDAR antagonist, displayed no influence on the induction of LTD. These results suggest that the induction of LTD in layer II/III pyramidal neurons of the young rat visual cortex is NMDAR-dependent and requires NR2B-containing NMDARs, not NR2A-containing NMDARs.