Research Article

NMDA Receptor-Dependent Metaplasticity by High-Frequency Magnetic Stimulation

Figure 1

Electrical stimulation-induced LTP is lost after HFMS priming. (A1) Experimental paradigm showing the timepoints of high-frequency magnetic stimulation (HFMS) and conditioning stimulation (CS). Application of the mGluR blockers MSOP and MCPG is indicated by the gray bar. (A2) Sample traces of timepoints ① and ② in naive slices (control), in HFMS-primed slices, and under mGluR-blocking conditions. (A3) Time course of electrical stimulation-induced plasticity with (closed circles) or without (open circles) priming with high-frequency magnetic stimulation (HFMS). A subset of slices was bathed in MSOP and MCPG during HFMS and CS (gray circles). Baseline recording was started 20 min after priming stimulation using the following HFMS paradigm: 10 bursts (1 s apart) of 20 pulses at 100 Hz with 5 repetitions (10 s apart) as previously published [8]. At 30 min after HFMS (i.e., after 10 min baseline recording), slices were electrically stimulated (conditioning stimulation, CS) using a paradigm composed of 10 trains of 20 pulses at 100 Hz (1 s apart) at time point 0 min (gray arrow). (A4) Percentage of mean fEPSP slopes calculated during 56–60 min after CS application. Significant LTP was induced by the CS paradigm in control slices without priming stimulation (open bar). In contrast, a significant LTD, but not LTP, was induced in slices with priming HFMS (closed bar). MSOP/MCPG application did not alter LTP in naive slices (M/M) but prevented CS-induced LTD in HFMS-primed slices (M/M-HFMS). (b) Paired-pulse plasticity in control experiments (B1), metaplasticity experiments in standard solution (B2), and metaplasticity experiments in mGluR-blocking conditions (B3).
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