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Neonatal seizures alter NMDA glutamate receptor GluN2A and 3A subunit expression and function in hippocampal CA1 neurons.

Zhou C, Sun H, Klein PM, Jensen FE - Front Cell Neurosci (2015)

Bottom Line: Moreover, GluN eEPSCs showed a decreased sensitivity to GluN2B selective antagonists and decreased Mg(2+) sensitivity at negative holding potentials, indicating a higher proportion of GluN2A and GluN3A subunit function, respectively.These physiological findings were accompanied by a concurrent increase in GluN2A phosphorylation and GluN3A protein.These results suggest that altered GluN function and expression could potentially contribute to future epileptogenesis following neonatal seizures, and may represent potential therapeutic targets for the blockade of future epileptogenesis in the developing brain.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurology, Division of Neuroscience, Boston Children's Hospital Boston, MA, USA ; Program in Neurobiology, Harvard Medical School Boston, MA, USA.

ABSTRACT
Neonatal seizures are commonly caused by hypoxic and/or ischemic injury during birth and can lead to long-term epilepsy and cognitive deficits. In a rodent hypoxic seizure (HS) model, we have previously demonstrated a critical role for seizure-induced enhancement of the AMPA subtype of glutamate receptor (GluA) in epileptogenesis and cognitive consequences, in part due to GluA maturational upregulation of expression. Similarly, as the expression and function of the N-Methyl-D-aspartate (NMDA) subtype of glutamate receptor (GluN) is also developmentally controlled, we examined how early life seizures during the critical period of synaptogenesis could modify GluN development and function. In a postnatal day (P)10 rat model of neonatal seizures, we found that seizures could alter GluN2/3 subunit composition of GluNs and physiological function of synaptic GluNs. In hippocampal slices removed from rats within 48-96 h following seizures, the amplitudes of synaptic GluN-mediated evoked excitatory postsynaptic currents (eEPSCs) were elevated in CA1 pyramidal neurons. Moreover, GluN eEPSCs showed a decreased sensitivity to GluN2B selective antagonists and decreased Mg(2+) sensitivity at negative holding potentials, indicating a higher proportion of GluN2A and GluN3A subunit function, respectively. These physiological findings were accompanied by a concurrent increase in GluN2A phosphorylation and GluN3A protein. These results suggest that altered GluN function and expression could potentially contribute to future epileptogenesis following neonatal seizures, and may represent potential therapeutic targets for the blockade of future epileptogenesis in the developing brain.

No MeSH data available.


Related in: MedlinePlus

Reduction of Mg2+-sensitivity of GluN eEPSCs at 48–96 h in hippocampal CA1 neurons following HS. (A,B) Representative traces of evoked GluN EPSCs (left panels) at a holding potential from −80 mV to +50 mV in ACSF with/without Mg2+ (1.2 mM) in CA1 pyramidal neurons in slices from control and 96 h post-HS rats. Right panels, corresponding I-V plots of the peak amplitudes of GluN eEPSCs. (C) GluN eEPSC I-V curves (with 1.2 mM Mg2+ in ACSF) and corresponding fitted Woodhull curves in CA1 pyramidal neurons in slices from control (empty circles) and 96 h post-HS rats (filled circles). (D) Group data of fitted Woodhull Kd values in CA1 pyramidal neurons in slices from 1–24 h (n = 10 cells), 48–96 h (n = 12 cells), 1 week post-HS (n = 5 cells) and littermate control rats (n = 5–11 cells). *p < 0.05. Error bars indicate S.E.M.
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Figure 4: Reduction of Mg2+-sensitivity of GluN eEPSCs at 48–96 h in hippocampal CA1 neurons following HS. (A,B) Representative traces of evoked GluN EPSCs (left panels) at a holding potential from −80 mV to +50 mV in ACSF with/without Mg2+ (1.2 mM) in CA1 pyramidal neurons in slices from control and 96 h post-HS rats. Right panels, corresponding I-V plots of the peak amplitudes of GluN eEPSCs. (C) GluN eEPSC I-V curves (with 1.2 mM Mg2+ in ACSF) and corresponding fitted Woodhull curves in CA1 pyramidal neurons in slices from control (empty circles) and 96 h post-HS rats (filled circles). (D) Group data of fitted Woodhull Kd values in CA1 pyramidal neurons in slices from 1–24 h (n = 10 cells), 48–96 h (n = 12 cells), 1 week post-HS (n = 5 cells) and littermate control rats (n = 5–11 cells). *p < 0.05. Error bars indicate S.E.M.

Mentions: Mg2+ sensitivity is one of the critical factors affecting GluN function, and determined by GluN subunit composition (Zhou et al., 2009) as well as post-translational modification (Chen and Huang, 1992). GluN3A subunit confers decreased Mg2+ sensitivity and is developmentally upregulated in the first 2 postnatal weeks (Zhou et al., 2009). We thus examined the Mg2+-sensitivity of GluN eEPSCs in CA1 pyramidal neurons within postnatal period P12–14 by evoking EPSCs at holding potentials from −80 through +50 mV and measuring linear I-V curves in Mg2+-free ACSF. With 1.2 mM Mg2+ added into ACSF, inward currents at holding potentials from −80 to 0 mV were suppressed and maximal inward currents appeared at around −30 or −20 mV, exhibiting a typical J-shape I-V curve (Figure 4A). In contrast to age-matched controls (−16.53 ± 4.12 pA, n = 7 cells), maximal inward currents at a holding potential of −30 mV in 48–96 h post-HS rats (−36.85 ± 7.31pA, n = 7 cells) were significantly larger (Figure 4), suggesting that Mg2+ sensitivity of GluNs in post-HS rats is decreased (t-test, p = 0.032).


Neonatal seizures alter NMDA glutamate receptor GluN2A and 3A subunit expression and function in hippocampal CA1 neurons.

Zhou C, Sun H, Klein PM, Jensen FE - Front Cell Neurosci (2015)

Reduction of Mg2+-sensitivity of GluN eEPSCs at 48–96 h in hippocampal CA1 neurons following HS. (A,B) Representative traces of evoked GluN EPSCs (left panels) at a holding potential from −80 mV to +50 mV in ACSF with/without Mg2+ (1.2 mM) in CA1 pyramidal neurons in slices from control and 96 h post-HS rats. Right panels, corresponding I-V plots of the peak amplitudes of GluN eEPSCs. (C) GluN eEPSC I-V curves (with 1.2 mM Mg2+ in ACSF) and corresponding fitted Woodhull curves in CA1 pyramidal neurons in slices from control (empty circles) and 96 h post-HS rats (filled circles). (D) Group data of fitted Woodhull Kd values in CA1 pyramidal neurons in slices from 1–24 h (n = 10 cells), 48–96 h (n = 12 cells), 1 week post-HS (n = 5 cells) and littermate control rats (n = 5–11 cells). *p < 0.05. Error bars indicate S.E.M.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4585040&req=5

Figure 4: Reduction of Mg2+-sensitivity of GluN eEPSCs at 48–96 h in hippocampal CA1 neurons following HS. (A,B) Representative traces of evoked GluN EPSCs (left panels) at a holding potential from −80 mV to +50 mV in ACSF with/without Mg2+ (1.2 mM) in CA1 pyramidal neurons in slices from control and 96 h post-HS rats. Right panels, corresponding I-V plots of the peak amplitudes of GluN eEPSCs. (C) GluN eEPSC I-V curves (with 1.2 mM Mg2+ in ACSF) and corresponding fitted Woodhull curves in CA1 pyramidal neurons in slices from control (empty circles) and 96 h post-HS rats (filled circles). (D) Group data of fitted Woodhull Kd values in CA1 pyramidal neurons in slices from 1–24 h (n = 10 cells), 48–96 h (n = 12 cells), 1 week post-HS (n = 5 cells) and littermate control rats (n = 5–11 cells). *p < 0.05. Error bars indicate S.E.M.
Mentions: Mg2+ sensitivity is one of the critical factors affecting GluN function, and determined by GluN subunit composition (Zhou et al., 2009) as well as post-translational modification (Chen and Huang, 1992). GluN3A subunit confers decreased Mg2+ sensitivity and is developmentally upregulated in the first 2 postnatal weeks (Zhou et al., 2009). We thus examined the Mg2+-sensitivity of GluN eEPSCs in CA1 pyramidal neurons within postnatal period P12–14 by evoking EPSCs at holding potentials from −80 through +50 mV and measuring linear I-V curves in Mg2+-free ACSF. With 1.2 mM Mg2+ added into ACSF, inward currents at holding potentials from −80 to 0 mV were suppressed and maximal inward currents appeared at around −30 or −20 mV, exhibiting a typical J-shape I-V curve (Figure 4A). In contrast to age-matched controls (−16.53 ± 4.12 pA, n = 7 cells), maximal inward currents at a holding potential of −30 mV in 48–96 h post-HS rats (−36.85 ± 7.31pA, n = 7 cells) were significantly larger (Figure 4), suggesting that Mg2+ sensitivity of GluNs in post-HS rats is decreased (t-test, p = 0.032).

Bottom Line: Moreover, GluN eEPSCs showed a decreased sensitivity to GluN2B selective antagonists and decreased Mg(2+) sensitivity at negative holding potentials, indicating a higher proportion of GluN2A and GluN3A subunit function, respectively.These physiological findings were accompanied by a concurrent increase in GluN2A phosphorylation and GluN3A protein.These results suggest that altered GluN function and expression could potentially contribute to future epileptogenesis following neonatal seizures, and may represent potential therapeutic targets for the blockade of future epileptogenesis in the developing brain.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurology, Division of Neuroscience, Boston Children's Hospital Boston, MA, USA ; Program in Neurobiology, Harvard Medical School Boston, MA, USA.

ABSTRACT
Neonatal seizures are commonly caused by hypoxic and/or ischemic injury during birth and can lead to long-term epilepsy and cognitive deficits. In a rodent hypoxic seizure (HS) model, we have previously demonstrated a critical role for seizure-induced enhancement of the AMPA subtype of glutamate receptor (GluA) in epileptogenesis and cognitive consequences, in part due to GluA maturational upregulation of expression. Similarly, as the expression and function of the N-Methyl-D-aspartate (NMDA) subtype of glutamate receptor (GluN) is also developmentally controlled, we examined how early life seizures during the critical period of synaptogenesis could modify GluN development and function. In a postnatal day (P)10 rat model of neonatal seizures, we found that seizures could alter GluN2/3 subunit composition of GluNs and physiological function of synaptic GluNs. In hippocampal slices removed from rats within 48-96 h following seizures, the amplitudes of synaptic GluN-mediated evoked excitatory postsynaptic currents (eEPSCs) were elevated in CA1 pyramidal neurons. Moreover, GluN eEPSCs showed a decreased sensitivity to GluN2B selective antagonists and decreased Mg(2+) sensitivity at negative holding potentials, indicating a higher proportion of GluN2A and GluN3A subunit function, respectively. These physiological findings were accompanied by a concurrent increase in GluN2A phosphorylation and GluN3A protein. These results suggest that altered GluN function and expression could potentially contribute to future epileptogenesis following neonatal seizures, and may represent potential therapeutic targets for the blockade of future epileptogenesis in the developing brain.

No MeSH data available.


Related in: MedlinePlus