Figure 1.

Prolonged IH exposure attenuates LTP within the dentate gyrus. A, LTP of the fEPSP following HFS in control (blue circles; n = 9 slices, 7 animals), IH₁₀ (yellow triangles; n = 4 slices, 2 animals), IH₂₀ (magenta diamonds; n = 8 slices, 3 animals), and IH₃₀ (red squares; n = 10 slices, 7 animals) illustrate differences in potentiation following HFS. Representative traces of evoked fEPSPs are shown above the graph with baseline (black trace) and post-HFS induction indicated (color traces: control, blue; IH₁₀, yellow; IH₂₀, magenta; IH₃₀, red). Arrows at the bottom indicate the time sampled for B and C. Calibration: 0.2 mV, 10 ms. B, Immediately following HFS, a difference among groups was observed (F_(3,27) = 6.667, p = 0.0016). A post hoc Dunnett's test revealed no difference immediately following HFS between control and IH₁₀ groups, yet did in both IH₂₀ and IH₃₀ groups in the fEPSP slope when compared with control. C, Sixty minutes post-HFS, a difference among groups was detected (F_(3,27) = 9.529, p = 0.0002). Post hoc Dunnett's test revealed that, while no difference was present between the control and IH₁₀ groups, the fEPSP in both the IH₂₀ and IH₃₀ groups was reduced compared with control group. In a subset of experiments (n = 4 slices, 3 animals), applying to a larger stimulation current during HFS did not to evoke LTP in the IH₃₀ group (B and C, white triangles). *p < 0.05.