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GluN2D-containing NMDA receptors-mediate synaptic currents in hippocampal interneurons and pyramidal cells in juvenile mice.

von Engelhardt J, Bocklisch C, Tönges L, Herb A, Mishina M, Monyer H - Front Cell Neurosci (2015)

Bottom Line: In contrast, much less is known about the role of GluN2D, which is expressed at low levels and is downregulated following the second postnatal week.The expression of the transgene was confined to hippocampal interneurons, most of which were parvalbumin- and/or somatostatin-positive.Electrophysiological and morphological analyses showed that GluN2D was present mainly in fast spiking basket and axo-axonic cells.

View Article: PubMed Central - PubMed

Affiliation: Synaptic Signalling and Neurodegeneration, German Cancer Research Center (DKFZ) Heidelberg, Germany ; Synaptic Signalling and Neurodegeneration, German Center for Neurodegenerative Diseases (DZNE) Bonn, Germany.

ABSTRACT
The differential regulation of the two major N-methyl-D-aspartate receptor (NMDAR) subunits GluN2A and GluN2B during development in forebrain pyramidal cells has been thoroughly investigated. In contrast, much less is known about the role of GluN2D, which is expressed at low levels and is downregulated following the second postnatal week. However, it appears that few cells, presumably interneurons, continue to express GluN2D also in juvenile mice. To investigate which hippocampal cell types express this subunit, we generated transgenic mice with EGFP-tagged GluN2D receptors. The expression of the transgene was confined to hippocampal interneurons, most of which were parvalbumin- and/or somatostatin-positive. Electrophysiological and morphological analyses showed that GluN2D was present mainly in fast spiking basket and axo-axonic cells. Based on pharmacological evidence and electrophysiological analysis of GluN2D knockout mice, we conclude that GluN2D-containing NMDARs mediate synaptic currents in hippocampal interneurons of young and juvenile mice and in CA1 pyramidal neurons of newborn mice.

No MeSH data available.


Related in: MedlinePlus

Effects of ifenprodil on NMDAR-mediated EPSCs in P9-12 PV-EGFP-positive cells. (A) Example traces of NMDAR-mediated EPSCs before and after application of ifenprodil. EPSCs were recorded in CA1 PV-EGFP interneurons of P9-12 mice. The quantification of the remaining current after ifenprodil application shows that NMDARs containing other subunits than GluN2B contribute to synaptic currents. (B) Example traces of NMDAR-mediated EPSCs before and after ifenprodil application normalized to the peak. The quantification of EPSC τdecay shows that NMDARs with slower decay kinetics than that of diheteromeric GluN2B-containing NMDARs contribute to synaptic currents in PV-EGFP interneurons in P9-12 mice. *p < 0.05.
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Figure 8: Effects of ifenprodil on NMDAR-mediated EPSCs in P9-12 PV-EGFP-positive cells. (A) Example traces of NMDAR-mediated EPSCs before and after application of ifenprodil. EPSCs were recorded in CA1 PV-EGFP interneurons of P9-12 mice. The quantification of the remaining current after ifenprodil application shows that NMDARs containing other subunits than GluN2B contribute to synaptic currents. (B) Example traces of NMDAR-mediated EPSCs before and after ifenprodil application normalized to the peak. The quantification of EPSC τdecay shows that NMDARs with slower decay kinetics than that of diheteromeric GluN2B-containing NMDARs contribute to synaptic currents in PV-EGFP interneurons in P9-12 mice. *p < 0.05.

Mentions: EGFP-GluN2D expression in transgenic mice might result in a non-physiological expression of tagged GluN2D in synapses of fluorescent cells. Double labeling experiments showed that all hippocampal PV-expressing interneurons co-expressed EGFP-GluN2D. To corroborate our results obtained from EGFP-GluN2D mice, we investigated PV-positive cells that do not express EGFP-GluN2D. To this end, we took advantage of a transgenic mouse line in which PV-positive cells are labeled by EGFP (PV-EGFP mice) (Meyer et al., 2002). We could not analyze PV-positive cells in P3-5 mice, since there were no green cells at this age consistent with the appearance of PV expression only during the 2nd postnatal week (Nitsch et al., 1990). In PV-positive cells of P9-12 PV-EGFP mice, ifenprodil application resulted in a 50% reduction in NMDAR-mediated EPSC amplitude (Figure 8A, Table 3). Importantly, ifenprodil significantly increased τdecay of NMDAR-mediated EPSCs in EGFP-positive interneurons in the CA1 region (Figure 8B, Table 3). These results demonstrate that NMDAR subunits with decay kinetics slower than those of GluN1/GluN2B diheteromeric NMDARs (i.e., GluN2D containing NMDARs) are present in the synapse of PV-positive interneurons.


GluN2D-containing NMDA receptors-mediate synaptic currents in hippocampal interneurons and pyramidal cells in juvenile mice.

von Engelhardt J, Bocklisch C, Tönges L, Herb A, Mishina M, Monyer H - Front Cell Neurosci (2015)

Effects of ifenprodil on NMDAR-mediated EPSCs in P9-12 PV-EGFP-positive cells. (A) Example traces of NMDAR-mediated EPSCs before and after application of ifenprodil. EPSCs were recorded in CA1 PV-EGFP interneurons of P9-12 mice. The quantification of the remaining current after ifenprodil application shows that NMDARs containing other subunits than GluN2B contribute to synaptic currents. (B) Example traces of NMDAR-mediated EPSCs before and after ifenprodil application normalized to the peak. The quantification of EPSC τdecay shows that NMDARs with slower decay kinetics than that of diheteromeric GluN2B-containing NMDARs contribute to synaptic currents in PV-EGFP interneurons in P9-12 mice. *p < 0.05.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4373385&req=5

Figure 8: Effects of ifenprodil on NMDAR-mediated EPSCs in P9-12 PV-EGFP-positive cells. (A) Example traces of NMDAR-mediated EPSCs before and after application of ifenprodil. EPSCs were recorded in CA1 PV-EGFP interneurons of P9-12 mice. The quantification of the remaining current after ifenprodil application shows that NMDARs containing other subunits than GluN2B contribute to synaptic currents. (B) Example traces of NMDAR-mediated EPSCs before and after ifenprodil application normalized to the peak. The quantification of EPSC τdecay shows that NMDARs with slower decay kinetics than that of diheteromeric GluN2B-containing NMDARs contribute to synaptic currents in PV-EGFP interneurons in P9-12 mice. *p < 0.05.
Mentions: EGFP-GluN2D expression in transgenic mice might result in a non-physiological expression of tagged GluN2D in synapses of fluorescent cells. Double labeling experiments showed that all hippocampal PV-expressing interneurons co-expressed EGFP-GluN2D. To corroborate our results obtained from EGFP-GluN2D mice, we investigated PV-positive cells that do not express EGFP-GluN2D. To this end, we took advantage of a transgenic mouse line in which PV-positive cells are labeled by EGFP (PV-EGFP mice) (Meyer et al., 2002). We could not analyze PV-positive cells in P3-5 mice, since there were no green cells at this age consistent with the appearance of PV expression only during the 2nd postnatal week (Nitsch et al., 1990). In PV-positive cells of P9-12 PV-EGFP mice, ifenprodil application resulted in a 50% reduction in NMDAR-mediated EPSC amplitude (Figure 8A, Table 3). Importantly, ifenprodil significantly increased τdecay of NMDAR-mediated EPSCs in EGFP-positive interneurons in the CA1 region (Figure 8B, Table 3). These results demonstrate that NMDAR subunits with decay kinetics slower than those of GluN1/GluN2B diheteromeric NMDARs (i.e., GluN2D containing NMDARs) are present in the synapse of PV-positive interneurons.

Bottom Line: In contrast, much less is known about the role of GluN2D, which is expressed at low levels and is downregulated following the second postnatal week.The expression of the transgene was confined to hippocampal interneurons, most of which were parvalbumin- and/or somatostatin-positive.Electrophysiological and morphological analyses showed that GluN2D was present mainly in fast spiking basket and axo-axonic cells.

View Article: PubMed Central - PubMed

Affiliation: Synaptic Signalling and Neurodegeneration, German Cancer Research Center (DKFZ) Heidelberg, Germany ; Synaptic Signalling and Neurodegeneration, German Center for Neurodegenerative Diseases (DZNE) Bonn, Germany.

ABSTRACT
The differential regulation of the two major N-methyl-D-aspartate receptor (NMDAR) subunits GluN2A and GluN2B during development in forebrain pyramidal cells has been thoroughly investigated. In contrast, much less is known about the role of GluN2D, which is expressed at low levels and is downregulated following the second postnatal week. However, it appears that few cells, presumably interneurons, continue to express GluN2D also in juvenile mice. To investigate which hippocampal cell types express this subunit, we generated transgenic mice with EGFP-tagged GluN2D receptors. The expression of the transgene was confined to hippocampal interneurons, most of which were parvalbumin- and/or somatostatin-positive. Electrophysiological and morphological analyses showed that GluN2D was present mainly in fast spiking basket and axo-axonic cells. Based on pharmacological evidence and electrophysiological analysis of GluN2D knockout mice, we conclude that GluN2D-containing NMDARs mediate synaptic currents in hippocampal interneurons of young and juvenile mice and in CA1 pyramidal neurons of newborn mice.

No MeSH data available.


Related in: MedlinePlus