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. 2007 Dec 12;27(50):13706–13718. doi: 10.1523/JNEUROSCI.3503-07.2007

Figure 2.

Figure 2.

Synaptic insertion of GluR1 and actin polymerization is necessary to permit stable spine enlargement after chemically induced LTP. A1–A3, CA1 neurons from organotypic hippocampal slice cultures expressing SEP-GluR1(wt) and tDimer, a red cytoplasmic marker (n = 200 spines; 3 cells) [data taken from the study by Kopec et al. (2006) for comparison with subsequent data], or tDimer alone and exposed to 1 μm Cytochalasin D 10 min before and during the entire imaging protocol (n = 120 spines; 3 cells). A1, Mean spine volume (integrated red fluorescence) and spine surface receptor (integrated green fluorescence) relative to chemLTP induction. ChemLTP drug exposure is indicated by a black bar. Values normalized to −10 min time point are shown (*p < 0.05). A2, Sample images obtained at indicated times relative to chemLTP induction (red channel only). Images are maximum value projection of three to four consecutive stacks. Blue arrowheads indicate spines that have enlarged, and orange arrowheads indicate spines that have shrunk. A3, Sample images, red channel only, for cells exposed to Cytochalasin D. B1, B2, Same as A for neurons expressing SEP-GluR1(T887A) and tDimer (n = 178 spines; 3 cells). B3, Paired whole-cell recordings of AMPAR- and NMDAR-mediated currents from uninfected cells and neighboring infected cells expressing GluR1 (T887A). AMPA component is defined as peak amplitude at −60 mV holding potential. NMDA component is defined as mean amplitude from 150–160 ms after peak at +40 mV holding potential. Gray points, Individual data points; pink point, mean data point (n = 9 pairs). C1, C2, Same as A for neurons expressing SEP-GluR1(3A) and tDimer (n = 187 spines; 3 cells). C3, Same as B3 for neurons expressing SEP-GLuR1(3A). C4, LTP is blocked in cells expressing SEP-GluR1(3A) compared with SEP-GluR1(wt), GluR1(wt) (n = 9), and GluR1(3A) (n = 8). LTP induction (3 min pairing protocol, 3 Hz, 0 mV holding potential) is indicated by a black bar (*p = 0.05). D, Cumulative distribution of fold spine volume change during chemLTP from cells expressing SEP-GluR1 (wt), (T887A), or (3A). Fold volume change defined as mean volume (+40 and +70 min time points)/mean volume (−30 and −10 min time points). Error bars represent SEM. Scale bar, 1 μm.