Figure 2.

PSs with different frequencies exert differential influences on subsequent LTD induction. A, B, Summary graphs comparing LTD in CA1 cells primed with 600 pulses of 1 Hz (A; n = 7) or 5 Hz (B; n = 8) LPS with LTD in interleaved control cells without PSs. PSs were applied ∼20 min before the baseline recording. LTD was induced in CA1 neurons with 300 synaptic stimuli of the Schaffer fibers at 1 Hz during depolarization to −45 mV in the presence of the GABA_A antagonist BMI (10 μm). Obviously, 1 or 5 Hz LPS suppressed subsequent LTD induction by decreasing the depression magnitude. Filled arrows refer to the time points when the PSs were delivered. Open arrows refer to the time points when the LTD-producing pairing protocols were applied. C, D, Summary graphs comparing LTD in cells primed with 600 pulses of 10 Hz (C; n = 7) and 20 Hz (D; n = 7) PSs with LTD in interleaved control cells without PSs. The 10 and 20 Hz PSs failed to exert any significant effect on the subsequent LTD induction. E, F, Summary graphs comparing LTP in CA1 cells primed with 600 pulses of 50 Hz (E; n = 7) or 100 Hz (F; n = 8) HPS with LTD in interleaved control cells without PSs. The 50 and 100 Hz HPS facilitated subsequent LTD induction by increasing the depression magnitude. G, Summary of data comparing LTD in cells primed with PSs at different frequencies. ***p < 0.001, ANOVA post hoc LSD test versus control. H, Cumulative distributions of normalized EPSCs in cells priming with different stimulations and in interleaved control cells without PSs. Norm., Normalized; con., control.