MML-LTP induction at 16 dpi inhibits the later spinogenesis of new neurons specifically in MML.

<p>(<b>A</b>) Experimental schedules for <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0045270#pone-0045270-g003" target="_blank">Figure 3</a>. Insets are samples of evoked field potential traces that are recorded at pre-HFS, 1 day, and 12 days post-HFS. (<b>B</b>) PS amplitudes of the DG obtained from rats used for experiments in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0045270#pone-0045270-g003" target="_blank">Figure 3</a>. Pre- and post-HFS delivery are indicated by “pre” and “post”, respectively. (<b>C</b>) Fluorescence micrographs of F-actin signal (phalloidin-TRITC, red) in control (<b>C1</b>) and LTP-induced DG (<b>C2</b>) of 28-dpi animals. Nuclear signal is shown in blue (DRAQ5). (<b>D</b>) Synaptophysin (red) and nuclei (DRAQ5, blue) signals of control (<b>D1</b>) and LTP hemispheres (<b>D2</b>). Scale bars for (<b>C</b>) and (<b>D</b>), 50 µm. (<b>E, F</b>) Representative z-stack images of dendritic segments of new neurons at 28 dpi in control (<b>E1, F1</b>) and LTP hemispheres (<b>E2, F2</b>). (<b>E1, 2</b>) and (<b>F1, 2</b>) represent micrographs of OML and MML, respectively. Only (<b>F2</b>) represents a dendritic segment within the LTP-induced layer, indicated by red characters. Scale bar, 2 µm. (<b>G</b>) Graphs of average F-actin intensity in each DG layer in arbitrary units (AU). *, <i>P</i><0.02 from Student’s t-test. (<b>H</b>) Graph shows the MML-to-OML ratio (MML/OML) of average synaptophysin intensity. (<b>I</b>) Spine density within the LTP-induced layer significantly decreases compared with other layers. Spine number per 10-µm dendritic fragment in each layer is graphed. (<b>J</b>) Graph shows MML-to-OML ratio (MML/OML) of spine density in control and LTP hemispheres. (<b>K</b>) Average spine cross-sectional area is indicated. (<b>G, K</b>) Dendritic fragments for spine analyses: control hemisphere, n = 18, LTP hemisphere, n = 18 from 3 animals. Data from the LTP-induced layer are indicated by red color in each graph. n.s. indicates no significant difference or variance. <i>P</i> values from post-hoc Fisher’s test, Scheffe’s test, and Student’s t-test are shown in (<b>G</b>), (<b>I</b>), and (<b>J</b>), respectively.