Modeling of the Complex of the N-Methyl–D-Aspartate (NMDA) Receptor with Lipids of the Postsynaptic Membrane

The N-methyl-d-aspartate (NMDA) receptor has been implicated in the formation of synaptic connections. To investigate the role of the ε2 (NR2B) NMDA receptor subunit, which is prominently expressed during early development, we used neurons from mice lacking this subunit. Although ε2−/− mice die soon after birth, we examined whether NMDA receptor targeting to the postsynaptic membrane was dependent on the ε2 subunit by rescuing hippocampal neurons from these mice and studying them in autaptic cultures. In voltage-clamp recordings, excitatory postsynaptic currents (EPSCs) from ε2−/− neurons expressed an NMDA receptor–mediated EPSC that was apparent as soon as synaptic activity developed. However, compared with wild-type neurons, NMDA receptor–mediated EPSC deactivation kinetics were much faster and were less sensitive to glycine, but were blocked by Mg2+ or AP5. Whole cell currents from ε2−/− neurons were also more sensitive to block by low concentrations of Zn2+ and much less sensitive to the ε2-specific antagonist ifenprodil than wild-type currents. The rapid NMDA receptor–mediated EPSC deactivation kinetics and the pharmacological profile from ε2−/−neurons are consistent with the expression of ζ1/ε1 diheteromeric receptors in excitatory hippocampal neurons from mice lacking the ε2 subunit. Thus ε1 can substitute for the ε2 subunit at synapses and ε2 is not required for targeting of NMDA receptors to the postsynaptic membrane.

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Glycine Binding Site of the Synaptic NMDA Receptor in Subpostremal NTS Neurons

Journal of Neurophysiology ◽

10.1152/jn.00927.2004 ◽

2005 ◽

Vol 94 (1) ◽

pp. 147-152 ◽

Cited By ~ 19

Author(s):

Vander Baptista ◽

Wamberto Antonio Varanda

Keyword(s):

Nmda Receptor ◽

Binding Site ◽

Reversal Potential ◽

Postsynaptic Membrane ◽

Bathing Solution ◽

Total Charge ◽

Dependent Manner ◽

Concentration Dependent Manner ◽

Autonomic Reflex ◽

Transverse Slice

The nucleus of the tractus solitarius (NTS) plays an important role in the control of several autonomic reflex functions and has glutamate and GABA as main neurotransmitters. In this work, we used patch-clamp recordings in transverse slice preparations from rats to study whether the glycine binding site of the N-methyl-d-aspartate (NMDA) receptor is saturated or not in neurons of the subpostremal NTS. Except at hyperpolarized voltages and close to the reversal potential, glycine potentiated the NMDA responses in a concentration-dependent manner. The total charge transferred by glutamatergic currents was enhanced by glycine (500 μM; from 28 ± 13 to 42 ± 18 pC at +50 mV, n = 7, P < 0.05). Glycine increased the conductance of the postsynaptic membrane, without altering its reversal potential, both in the presence (from 2.4 ± 0.06 to 3.4 ± 0.09 nS; n = 7) and absence (from 3.1 ± 0.06 to 4.4 ± 0.10 nS; n = 8) of Mg2+ in the bathing solution. d-serine, in the presence of strychnine, also increased the amplitude of the NMDA component (by 68 ± 19%, P < 0.05, n = 5). The membrane potential was hyperpolarized (16 ± 6 mV, n = 8) by glycine, suggesting the presence of inhibitory glycinergic receptors. Our results indicate that the glycine site of the NMDA receptor in neurons of the subpostremal NTS is not saturated and that glycine may act as a modulator of the NMDA transmission in this nucleus.

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Mouse model of anti-NMDA receptor post–herpes simplex encephalitis

Neurology Neuroimmunology & Neuroinflammation ◽

10.1212/nxi.0000000000000529 ◽

2018 ◽

Vol 6 (2) ◽

pp. e529 ◽

Cited By ~ 7

Author(s):

Jenny Linnoila ◽

Benjamin Pulli ◽

Thaís Armangué ◽

Jesús Planagumà ◽

Radha Narsimhan ◽

...

Keyword(s):

Herpes Simplex ◽

Nmda Receptor ◽

Western Blot ◽

Blot Analysis ◽

Western Blot Analysis ◽

Postsynaptic Membrane ◽

Confocal Imaging ◽

Serum Antibodies ◽

Nmdar Encephalitis ◽

Hsv 1

ObjectiveTo develop an endogenous rodent model of postinfectious anti-NMDA receptor (NMDAR) encephalitis.MethodsSix mice were inoculated intranasally with herpes simplex virus (HSV) 1 and subsequently treated with acyclovir for 2 weeks. Serum was collected at 3, 6, and 8 weeks postinoculation and tested for NMDAR antibodies through a cell-based assay. Eight weeks postinoculation, mice were killed and their brains were sectioned and immunostained with antibodies to postsynaptic density (PSD)-95 and NMDARs. Colocalization of hippocampal PSD-95 and NMDAR clusters, representing postsynaptic membrane NMDARs, was quantified via confocal imaging. Hippocampi were additionally analyzed for NMDAR and PSD-95 protein using Western blot analysis.ResultsFour of 6 mice (67%) developed serum antibodies to NMDARs: 1 at 3 weeks, 1 at 6 weeks, and 2 at 8 weeks postinoculation. As compared to inoculated mice that did not develop NMDAR antibodies, immunofluorescence staining revealed decreased hippocampal postsynaptic membrane NMDARs in mice with serum antibodies at 8 weeks postinoculation. Western blot analysis showed that mice that had NMDAR antibodies at 8 weeks had decreased total NMDAR but not PSD-95 protein in hippocampal extracts (p < 0.05).ConclusionsMice inoculated intranasally with HSV-1 developed serum NMDAR antibodies. These antibodies were associated with reduced hippocampal NMDARs, as has been shown in previous models where antibodies from patients with anti-NMDAR encephalitis were infused into mice, paving the way for future studies into the pathophysiology of autoimmune encephalitides.

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