Fig. 2.
Opposing effects of Aβ and Reelin on NMDA receptor tyrosine phosphorylation. (A) High doses of Aβ peptides prevent NMDA receptor phosphorylation in response to Reelin treatment. Acute WT hippocampal slices were incubated in the presence (R) or absence of Reelin (C) and Aβ25–35. NR2A and NR2B were immunoprecipitated from the homogenized lysates of the slices and analyzed for tyrosine phosphorylation. Total amounts of immunoprecipitated NR2A and NR2B are shown (NR2A, NR2B); one independent experiment is shown (n = 3). Tyrosine phosphorylation of NR2A and NR2B in the presence of Aβ and Reelin was not significantly different from control (lane 1) by paired t test. (B) Reelin enhances LTP in the absence of Aβ, but fails to rescue LTP suppression induced by high concentrations of Aβ25–35. (Upper) In WT hippocampal slices, Reelin (closed circles) enhances and Aβ25–35 (at 1 μM, open triangles) suppresses TBS-induced LTP compared with non-treated control slices (open squares). Reelin fails to restore LTP in the presence of high concentrations of Aβ (1 μM). Application of Reelin alone (closed circles) induces an immediate shift in baseline currents as a result of its direct effect on NMDA and AMPA receptor activity (21). (Lower) Statistical analysis of average LTP responses 30 to 35 min after TBS. Control LTP (open bar), 129.30% ± 14.16%, n = 2; Reelin (gray bar), 165.65% ± 14.11%, n = 2; high-dose Αβ25–35 (black closed bar), 99.85% ± 19.19%, n = 4; Reelin with high-dose Αβ25–35, 97.56% ± 6.83%, n = 4. ANOVA was performed, followed by Bonferroni post-test. Control compared with Reelin, P < 0.05; control compared with high-dose Aβ25–35, P < 0.05; high-dose Aβ25–35 compared with Reelin and Aβ25–35 together, P > 0.05. Asterisk denotes significance.