Figure 3.

Intrahippocampal Aβ injections altered synaptic variability and impaired LTP in cCA3-to-CA1 synapse. Temporal evolution of slope variability (a) and magnitude (b) of cCA3 stimulation-evoked EPSP in CA1 recorded along three consecutive experimental stages, from left to right: (1) 30 min before peptide injection (baseline), (2) 30 min after intrahippocampal injection, and (3) after HFS (six 1 s, 100 Hz trains, delivered every 60 s). EPSP variability increased after intrahippocampal injection, being significantly higher in the Aβ_1-40 group. HFS induced significant LTP in vehicle-injected subjects but not in Aβ-injected ones. In (a), each dot represents 5 min variance of slope; in (b), each dot illustrates 2 min mean ± standard error of the mean (SEM). Inset in (b): left—representative whole CA1 fEPSP average from each experimental group evoked by I₅₀ stimuli delivered in contralateral CA3 (the region representing the monosynaptic component is outlined by a gray rectangular box); right—three sets of average traces (10 trials per average) of the monosynaptic component of cCA3 stimulation-evoked CA1 field potential obtained during baseline (thin line, dark colour), after intrahippocampal injection (intermediate line, intermediate colour), and after HFS (thick line, light colour) for each experimental group (control, blue; Aβ_25-35, red; and Aβ_1-40, black). ^∗∗∗Significant differences between groups (p < 0.001). Data from each experimental group were normalized respecting the average value obtained during the last 15 min of baseline.