Fig. 4: Persistent disruption of synaptic plasticity in APP transgenic rats by the glucocorticoid methylprednisolone.

A Study design: Transgenic rats (TG) received single daily s.c. injections of methylprednisolone (MPL either 50 mg/kg, closed circles, or 30 mg/kg, open circles) for 3 days. Strong high frequency conditioning stimulation (sHFS, arrow) was applied repeatedly in the hippocampus of freely behaving rats over a 2.5-month period. The time course of sHFS-induced potentiation from the same animals is displayed before (B, 0 month), 2 h after (C, 0.5 month), 1 (D, 1.5 month) and 2 (E, 2.5 month) months after the last injection, starting at 5 months. Red and blue colours indicate MPL 50 or MPL 30 treatments, respectively (online version only). Insets show representative field EPSP traces at the times indicated. Calibration bars: vertical, 1 mV; horizontal, 10 ms. The magnitude of potentiation 3 h post-sHFS (last 10 min) at the different recording sessions is plotted for TG MPL 50 (F) and TG MPL 30 (G) rats, for individuals (left hand panel) and groups (right hand panel). The ♯ symbol stands for a statistical comparison between pre- and 3 h post-HFS values at each recording session within one group (paired t test) whereas an * indicates a comparison between groups. The magnitude of LTP was not significantly different between recording sessions in TG MPL 30 group (p > 0.05; one-way ANOVA with repeated measures). In contrast, LTP was significantly inhibited at 1.5 and 2.5 month in TG MPL 50 group. One symbol, p < 0.05; two symbols, p < 0.01. Values are mean ± S.E.M. % pre-HFS baseline EPSP amplitude.