Figure 5
The BDNF-mimetic drug DHF stimulated TrkB signaling and rescued synaptic plasticity deficits in the hippocampus of Ts65Dn mice. (A) Left, representative immunoblot for phosphorylated (Tyr817) or total TrkB (full-length and truncated isoforms: FL and T, respectively) and Actin in protein extracts from hippocampal samples collected from Ts65Dn and WT mice 1 hour after acute administration of DHF (5 mg/kg) or vehicle. Right, quantification of P-TrkBTyr817 (expressed as percentage of vehicle-treated WT) did not show differences after acute DHF administration. Two-way ANOVA on ranked-transformed data: genotype [F1,68 = 0.099, P = 0.753]; treatment [F1,68 = 1.730, P = 0.193]; genotype x treatment [F1,68 = 0.061, P = 0.806]. (B) Left, representative immunoblot for phosphorylated or total TrkB and Actin in protein extracts from cortical samples collected from Ts65Dn and WT mice 1 hour after acute administration of DHF or vehicle. Right, quantification of P-TrkBTyr817 did not show differences after acute DHF administration. Two-way ANOVA: genotype [F1,68 = 0.315, P = 0.576]; treatment [F1,68 = 0.019, P = 0.892]; genotype x treatment [F1,68 = 0.081, P = 0.776]. (C) Left, representative immunoblot for phosphorylated or total TrkB and Actin in protein extracts from hippocampal samples collected from Ts65Dn and WT mice chronically treated for 4 weeks with DHF or vehicle. Right, quantification of P-TrkBTyr817 showed a significant increase in the hippocampus of DHF-treated Ts65Dn mice. Two-way ANOVA on ranked-transformed data: genotype [F1,41 = 2.383, P = 0.130]; treatment [F1,41 = 9.135, P = 0.004]; genotype x treatment [F1,41 = 0.302, P = 0.586]. (D) Left, representative immunoblot for phosphorylated or total TrkB and Actin in protein extracts from cortical samples collected from Ts65Dn and WT mice chronically treated for 4 weeks with DHF or vehicle. Right, quantification of P-TrkBTyr817 did not show differences in the cortex of Ts65Dn and WT mice. Two-way ANOVA: genotype [F1,41 = 0.203, P = 0.665]; treatment [F1,41 = 1.570, P = 0.217]; genotype x treatment [F1,41 = 0.116, P = 0.686]. (E) Schematic representation of the experimental protocol and positioning of the stimulating and recording electrodes in hippocampal circuit for LTP at Shaffer collateral-CA1 synapses. (F) Average time course of the increase in the slope of fEPSP elicited in the CA1 Stratum Radiatum by stimulation of the Shaffer collateral in hippocampal slices obtained from Ts65Dn and WT mice. (G) Quantification of CA3-CA1 LTP. Two-way ANOVA: genotype [F1,24 = 8.459, P = 0.008]; treatment [F1,24 = 13.530, P = 0.001]; genotype x treatment [F1,24 = 0.0593, P = 0.810]. The number in parenthesis indicates the number of sample analyzed for each experimental group. *P < 0.05, Tukey post hoc test following two-way ANOVA. Full-length blots are presented in Supplementary Fig. 7.
