PT  - JOURNAL ARTICLE
AU  - Zhao, Jian-Ping
AU  - Constantine-Paton, Martha
TI  - <em>NR2A</em><sup>−/−</sup> Mice Lack Long-Term Potentiation But Retain NMDA Receptor and L-Type Ca<sup>2+</sup> Channel-Dependent Long-Term Depression in the Juvenile Superior Colliculus
AID  - 10.1523/JNEUROSCI.3153-07.2007
DP  - 2007 Dec 12
TA  - The Journal of Neuroscience
PG  - 13649--13654
VI  - 27
IP  - 50
4099  - http://www.jneurosci.org/content/27/50/13649.short
4100  - http://www.jneurosci.org/content/27/50/13649.full
SO  - J. Neurosci.2007 Dec 12; 27
AB  - Whether the subunit composition of NMDA receptors (NMDARs) controls the direction of long-term plasticity is currently disputed. In the visual layers of NR2A−/− juvenile superior colliculus (SC), synapses lose miniature NMDAR currents, leaving NR2B-rich receptors in extrasynaptic regions. Compared with wild type (WT), evoked NMDAR currents in mutant neurons have slower rise and decay times and lower NMDAR/AMPAR current ratios. Moreover, NMDAR and L-type Ca2+ channel-dependent SC long-term potentiation (LTP) is absent in NR2A−/− cells, whereas both WT and mutant neurons show long-duration, low-frequency-induced, long-term depression (LLF-LTD) that is blocked by either AP-5, nimodipine, or Ro 25-6981 [R-(R,S)-α-(4-hydroxyphenyl)-β-methyl-4-(phenylmethyl)-1-piperidine propranol]. Thus, NMDAR currents or signaling localized at the postsynaptic density are essential to SC NMDAR-dependent LTP, whereas extrasynaptic or NR2B-rich NMDARs are necessary for LLF-LTD. However, synaptic NMDARs as well as the NR2A subunit are missing in NR2A−/− mice. Therefore, NR2 subunit-specific ligand binding/channel properties and/or separate signaling pathways interacting with NMDARs at synaptic versus extrasynaptic receptors could underlie these results.