Figure 1.

p75^NTR modulation mitigates Aβ-induced loss of spines and neurite injury. (A–D) 21 DIV hippocampal neurons were treated with CM, Aβ, or Aβ with 100 nM LM11A-31 and examined at 24 h following treatment. (A) Representative neurons stained for drebrin (red). (B) Quantitation of numbers of drebrin-positive spines per length of dendrite segment, displayed in cumulative frequency and (inset) box plots, with p values above the boxes from KS testing of indicated comparisons. n = 24–38 neurites per condition from a total of 3 independent experiments. (C) Dendritic spines of EGFP-transfected hippocampal neurons (green) were visualized at 24 h post-Aβ exposure. (D) Dendritic spine density quantitated and displayed as in (B). n = 36–43 neurons per condition from a total of 9 independent experiments. (E,F) 7.5–8.0-month-old non-transgenic mice (Ntg) and AβPP^L/S mice (Tg) were treated with either vehicle (V) or LM11A-31 (C31) by oral gavage for 3 months, at which time spine density of hippocampal CA1 neurons was determined in Golgi-stained dendrites using MBF Neurolucida. (E) Representative traced dendritic spine images. (F) Quantitative analysis of the dendritic spine density displayed as in (B). 3 neurons from each of 6 mice were analyzed from each treatment group (n = 18/group). Scale bars in each image, 10 µm. To assess neuritic injury, neurons were immunostained for tau (red) and tubulin (green) and discrete yellow regions (‘beads’), reflecting co-accumulation of tau and tubulin, were manually counted and expressed as number of beads/100 µm neurite beads. Scale bar, 10 µm (G). (H) Cumulative frequency analysis shows a population of higher-count segments in Aβ-treated cells not observed in the presence of C31 or without Aβ. Inset displays box plots with p values from KS testing for the indicated comparisons. (I) Analysis of distributions of high-count segments (> 10 beads/100 µm). n = 12–14 neurites/group derived from a total three independent experiments.