Pretreatment with baicalein enhances long-term potentiation (LTP) in the hippocampal CA1 region. (A) Chemical structure of baicalein. (B) Baicalein (0.1, 1, 10 and 50 µM) had no effect on basal synaptic transmission. After establishing a stable field excitatory postsynaptic potential (fEPSP) baseline for 20 min, baicalein was perfused continuously (indicated by the bar) to individual slices. Insets, the sample traces before (1) or after (2) perfusion with baicalein. (C) Summary of averaged fEPSP slope from hippocampal slices incubated with different concentrations of baicalein (0.1, 1, 10 and 50 µM). No significant change was shown after drug application in each group, n= 6 for each group. The mean fEPSP slope before drug application (1 to 20 min) was normalized as 100% and the fEPSP slope at every time point was normalized to it. (D) Effect of baicalein (1 µM) on LTP in CA1 region of rat hippocampus. The superimposed fEPSPs in the upper portion show typical recordings from experiments taken at the time indicated by the number. (E) Summary data of the level of LTP 60 min after high-frequency stimulation (HFS) in the absence or presence of various concentrations of baicalein. *P < 0.05 versus control. Each point was the normalized mean ± SEM of 6–8 slices.