Figure 6

Adult selenium deficiency enhances synaptic transmission and inhibits long-term potentiation. (A) Input-output relationship of the slope of the CA1 field excitatory postsynaptic potential (fEPSP) in response to increasing stimulation of the Schaffer collateral fibers. Adult selenium deficiency increases evoked fEPSP slopes (Sepp1(+/+ 0Se) n = 11, (Sepp1(+/+ 1Se) n = 8). Nonlinear regression zero to top analysis confirms that the curves are different (p < 0.0001). (B) Relationship between the slope of the evoked fEPSPs from panel A and the corresponding fiber volley amplitude. Adult selenium deficiency increases the postsynaptic response to fixed presynaptic depolarization. Nonlinear regression zero to top analysis confirms that the curves are different, p < 0.0001) Inset: Representative traces of half the maximum fEPSP slope show a greater fEPSP slope for Sepp1(+/+ 0Se) slices (red) compared to Sepp1(+/+ 1Se) (blue) despite similar fiber volley amplitudes (dashed box). (C) Percent paired-pulse facilitation (PPF) achieved with increasing inter-pulse intervals. Adult selenium deficiency does not effect PPF (Sepp1(+/+ 0Se) n = 11, Sepp1(+/+ 1Se) n = 8). Inset: Representative PPF traces at 20 ms (blue) and 40 ms (red) inter-pulse intervals from (1) Sepp1(+/+ 1Se) slices and (2) Sepp1(+/+ 0Se) slices. (D) Long-term potentiation induced by high frequencystimulation (HFS: 100 Hz, 1 sec × 2, 20 sec interval). Sepp1(+/+ 0Se) slices fail to LTP following HFS (Sepp1(+/+ 0Se) n = 11, Sepp1(+/+ 1Se) n = 8; ANOVA p < 0.0001). Inset: Representative traces from (1) Sepp1(+/+ 1Se) slices and (2) Sepp1(+/+ 0Se) slices at time pints a, b and c (a: black-first baseline recording, b: red-2 min post HFS, c: blue-60 min post HFS). The same Sepp1(+/+ 1Se) from Figure 5 were compared with Sepp1(+/+ 0Se). All trace scale bars are 1 mV by 10 ms.