Figure 2. Aβ dimers are rapidly sequestered away from the hippocampal ISF in vivo to bind membranes.
(A) (Aβ1-40 S26C)2 dimers (40 nM) or Aβ1-40 monomers (8 nM) in test tubes were microdialyzed at 0.1, 0.4 and 1.0 μl/min and the resulting microdialysates were assessed using Aβ1-x ELISA. N=3 per group. (B) Aβ dimers or monomers were administered to living wt hippocampal ISF via a microdialysis cannula and post-injection ISF was collected at 0.4 μl/min for 1 h and analyzed for Aβ1-x. N=6 mice and N=5 mice for monomer- and dimer-injected. *: P=0.0126 by two-tailed Student's t test. (C) In vivo recovery of injected dimers was 8.85 ± 2.81% of that of injected monomers (N=5 pairs), in contrast to the in vitro paradigm (102 ± 11.4% (N=3 pairs)). ***: P<0.0001 by two-tailed Student's t test. (D) Representative hourly monitoring of injected Aβ monomers (blue triangle) or S26C Aβ dimers (red circle) in ISF of wt mice before and after injection. Inset shows values using a finer y-scale for t=2-5 h. (E) 320 pg Aβ monomers or S26C dimers were injected into hippocampi of wt mice and their brain homogenates were immediately fractionated for R1282 Aβ IP. WB: 3D6+6E10. Both monomers and dimers were recovered as monomers in the TBS and TBS-Tx. Representative of 4 experiments. (F) IP/WB quantification by ImageJ of N=8 mice injected side by side with monomers or dimers. Proportion of Aβ recovered in TBS-Tx vs TBS extracts post Aβ dimer injection was 23 ± 6.4 fold than that of Aβ monomer injection. ***: P<0.001 by 2-way ANOVA, followed by Bonferonni post-test. Value=mean ± SEM. See also Figure S2.