Figure 1.

High-frequency stimulation (HFS) elicits robust LTP that persists for over 24 h in vehicle-treated adult rats but not in Aβ-treated rats. (A,C) Acute injection of soluble Aβ oligomers resulted in impaired LTP in the dentate gyrus in vivo with regard to both population spike (PS) (A) and field excitatory postsynaptic potential (fEPSP) (C). (B,D) Figures show bar-charts representing pooled PS (B) and fEPSP (D) values from the graph shown in (A). The data summarize mean values during 6 time-points recorded pre-injection (baseline) and the 6 time-points after injection but prior to HFS (post-injection), as well as the mean values obtained 4 h and 24 h after HFS. The smaller bar-chart insets in each graph show the results of within-group comparisons. Significant within-group comparisons are indicated by lines drawn in the insets within parts (B,D). Significant between-group responses are marked with an asterisk (*) in (B,D). (C) Between-group comparison of PS amplitudes (C) revealed significantly lower values for Aβ-treated animals in the post injection time-period, as well as 4 h and 24 h after HFS. Within group comparisons of PS amplitudes (inset in C) revealed significantly higher values 24 h after HFS compared to the pre-injection and post-injection phases, and post-injection only, for control animals. The same pattern can be seen for the fEPSP responses for between-group and within-group comparisons. Pre-HFS baseline responses baselines did not differ between groups for either fEPSP or PS. (E) Original analog traces show representative field potentials evoked 5 min before, 5 min after, and 24 h after HFS from: (a) a vehicle-treated rat; and (b) an Aβ-treated rat. Vertical scale bar corresponds to 5 mV; horizontal scale bar corresponds to 5 ms.