Fig. 3. Xenon blocks formation of long-term potentiation (LTP) in the hippocampus. After 10 min of stable baseline recordings, high-frequency stimulation (HFS) was applied to the Schaffer collateral-associational commissural pathway, leading to increased field excitatory postsynaptic potential (fEPSP) slopes for at least 60 min. LTP was quantified by averaging the normalized fEPSP slopes during minutes 51–60 after HFS. Under control conditions, HFS led to LTP of 127.2 ± 5.8% (95% CI 121.8–132.6; n = 25; P < 0.001). During application of 1.9 mM xenon, fEPSP slopes returned to baseline level after 15–20 min, showing no LTP after 60 min (105.9 ± 2.9%; 95% CI 99.09–111.9; n = 25; P = 0.090 vs. fEPSP slopes during baseline period). Each symbol represents the averaged fEPSP slopes normalized with respect to the 10-min baseline period before HFS. Representative recording traces (insets ). § Stimulation artifact.