Fig. 2: AMPA receptor internalization is associated with both mGluR- and NMDAR-LTD. | Molecular Psychiatry

Fig. 2: AMPA receptor internalization is associated with both mGluR- and NMDAR-LTD.

From: Dissociation of functional and structural plasticity of dendritic spines during NMDAR and mGluR-dependent long-term synaptic depression in wild-type and fragile X model mice

Fig. 2

The content of AMPAR in the membrane surface of dendritic spines was monitored by measuring the fluorescence of SEP fused to the GluA2 subunit. Simultaneous field recordings and two-photon imaging were performed in the CA1 region of organotypic cultured hippocampal slices (CA3 removed) co-transfected with DsRed2 and SEP-GluA2. a–c Time-course of averaged fEPSP responses normalized to baseline. Representative fEPSP traces are shown at three time points: 15 min before, 15 and 60 min after LTD induction. Scale bar applies to all panels. a Application of vehicle (aCSF, 5 min, gray bars) did not alter fEPSP slope (10 min before vehicle: 104.28 ± 3.06% of total baseline; 50–60 min after vehicle: 105.03 ± 6.28%, n = 4, n.s. p = 0.916, paired t-test). b Bath application of NMDA (20 µM, 3 min) induced LTD of fEPSPs (10 min before NMDA: 99.25 ± 1.75% of total baseline; 50–60 min after NMDA: 75.62 ± 3.25%, n = 6, **p = 0.0023, paired t-test). c Bath application of DHPG (50 µ, 5 min) induced LTD of fEPSPs (before: 100.5 ± 3.38%; after DHPG: 56.38 ± 9.05%, n = 6; **p = 0.0048, paired t-test). d–f Time-course of the averaged spine volume (measured from DsRed2 fluorescence intensity) normalized to baseline. d Vehicle did not induce any persistent structural change in spine volume (before: 101.98 ± 0.25%; after vehicle: 95.72 ± 2.79%, n = 4; n.s. p = 0.096, paired t-test). e Spine volume persistently decreased upon NMDA application (before: 100.01 ± 1.09%; after NMDA: 71.47 ± 4.14%, n = 6; ***p = 0.0007, paired t-test). f DHPG did not induce any persistent structural change in spine volume (before: 100.6 ± 0.65%; after DHPG: 97.27 ± 8.35%, n = 6; n.s. p = 0.7221, paired t-test). g–i Time-course of the averaged fluorescence intensity of SEP-GluA2 in the spine, normalized to baseline. SEP fluorescence does not change after (g) vehicle application (before: 99.26 ± 2.78%; after vehicle 93.69 ± 2.86%, n = 4; n.s. p = 0.090, paired t-test), but persistently decreased after (h) NMDA application (before: 98.98 ± 0.77%; after NMDA: 57.37 ± 9.66%, n = 6; **p = 0.0075, paired t-test) and after (i) DHPG application (before: 99.64 ± 0.90%; after DHPG: 76.29 ± 7.61%, n = 6; *p = 0.0234, paired t-test). j–k Representative two-photon images of segments of secondary apical dendrites showing DsRed2 (magenta), SEP-GluA2 (green) and merged (yellow) fluorescence, at three times points (15 min before, 15 after, and 60 min after vehicle application or LTD induction). Scale bar applies to all panels. Yellow arrows indicate spines with no change in volume or AMPAR, orange arrows indicate spines showing AMPAR internalization or shrinkage, white arrows indicate spines showing AMPAR internalization but no shrinkage.

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