Glycine modulates synaptic NR2A- and NR2B-containing NMDA receptor-mediated responses in the rat visual cortex.
In the central nervous system, activation of N-methyl-d-aspartate receptor (NMDA-R) glycine binding sites is a prerequisite for activation of synaptic NMDA-Rs by the excitatory neurotransmitter glutamate. Here we used patch-clamp recordings in transverse slice preparations to study whether the glycine binding site of the NMDA-R saturates and to determine their subunit composition in layer II/III pyramidal neurons of the rat visual cortex. We found that the NMDA-R-mediated component of miniature excitatory postsynaptic currents (mEPSCs) could be potentiated by exogenously applied glycine. Similar results were obtained by exogenously applied d-serine. A specific antagonist for NR2B-NMDA-Rs, Ro 25-6981, reduced NMDA-R-mediated mEPSCs, and glycine with Ro 25-6981 enhanced NMDA-R-mediated mEPSCs. Moreover, Zn2+, an NR2A-NMDA-R antagonist, also reduced NMDA-mediated mEPSCs and glycine with Zn2+ enhanced the NMDA-mediated mEPSCs. Our data indicate that the glycine binding site of synaptic NR2A-containing and NR2B-containing NMDA-Rs does not saturate and that glycine may act as a modulator of NMDA-R-mediated transmission in layer II/III pyramidal neurons of the rat visual cortex.
Li
Yan-Hai
YH
Department of Physiology, School of Medicine, Xi'an Jiaotong University, Zhuque Dajie 205, Xi'an, Shannxi 710061, PR China.
Han
Tai-Zhen
TZ
D000818:Animals; D019706:Excitatory Postsynaptic Potentials / Q000502:physiology; D005998:Glycine / Q000378:metabolism*; D066298:In Vitro Techniques; D018408:Patch-Clamp Techniques; D021122:Protein Subunits / Q000502:physiology; D017966:Pyramidal Cells / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology; D018709:Statistics, Nonparametric; D013570:Synaptic Membranes / Q000378:metabolism; D014793:Visual Cortex / Q000166:cytology / Q000378:metabolism*
C120997:NR2A NMDA receptor; C121001:NR2B NMDA receptor; D021122:Protein Subunits; D016194:Receptors, N-Methyl-D-Aspartate; D005998:Glycine