LTP promotes neurogenesis of NSCs in cultures at least in part through BDNF-TrkB system.

<p>(<i>A</i>) cLTP increases the BDNF production in hippocampal cultures. Conditioned media was collected at 0, 10, 30, 60 min, and 1 day following cLTP induction. ELISA assays reveal a significant increase in the level of BDNF, but not NGF or NT-3, at 30 min and 1 hour following cLTP induction. *p<0.05, **p<0.01, n = 5 for each group. (<i>B</i>) cLTP-induced conditioned media activates membrane surface TrkB receptors in cultured NSC alone. Western blotting of surface biotinylated TrkB in NSCs sequentially probed with anti-TrkB tyrosine phosphorylation (p-TrkB) and anti-TrkB (TrkB) antibodies showing the increased level of receptor tyrosine phosphorylation by conditioned media from hippocampal cultures treated with cLTP protocol (cLTP), but not these treated with PBS (Control) and the increased phosphorylation was prevented in the presence of TrkB receptor inhibitor K252a (cLTP+200 nM). Data from 4 individual experiments were summarized in the bar graph at the bottom. **p<0.01, n = 4. (<i>C</i>) and (<i>D</i>) cLTP enhanced neurogenesis of NSCs in NSC-neuron co-cultures requires activation of TrkB receptors. Representative images (C) of GFP-labeled NSCs immunostained with MAP2 (red) illustrate cLTP increased, in a TrkB dependent fashion, both the total number of NSCs (green; summarized in the left Bar in D) and MAP2-positive NSCs (yellow; summarized in the right bar graph in D). **p<0.01, n = 6. Statistical analyses were performed with One Way ANOVA. Post hoc tests revealed a significant difference between conditioned media and other two group, and (<i>D</i>) the LTP group and two other groups. Data are mean ± SEM.