Fig. 5.

DCS effect on fEPSPs in apical CA1 and CA3 dendrites depends on the direction of efferent action potential (AP) propagation vector. A and B: positions of the DCS electrodes and approximate directions of the vectors of AP in Schaffer collaterals (black head arrow) and in mossy fibers (white head arrow). Stimulating Pt-Ir electrode is positioned at Schaffer collaterals in A and at mossy fibers in B. The recording glass electrodes are positioned at apical CA1 and apical CA3 dendrites. Numbers of slices for CA1 fEPSPs (in configuration A) are 6, 6, 5, and 6 for −200, −100, +100, and +200 μA of DCS, respectively. Numbers of slices for CA3 fEPSPs (in configuration B) are 7, 6, 7, and 7 for −200, −100, +100, and +200 μA of DCS, respectively. C: effect of DCS on fEPSPs at apical dendrite CA1 neurons (filled circles) is opposite to the effect on fEPSPs at apical dendrite CA3 neurons (open circles). Values of fEPSP slope for CA1 region are 84 ± 3, 88 ± 1, 117 ± 9, and 110 ± 8% for DCS of −200, −100, +100, and +200 μA, respectively. One-way ANOVA confirms significant fEPSP dependence on the DCS condition F(3,19) = 6.78; P < 0.003. Values of fEPSP slope for CA3 region are 78 ± 5, 95 ± 6, 108 ± 5, and 99 ± 5% for DCS of −200, −100, +100, and +200 μA, respectively. As above, one-way ANOVA demonstrates significant contribution of the DCS condition to the fEPSP slope, F(3,20) = 7.09; P = 0.002. ***P < 0.001, difference from baseline. §P < 0.05 and §§P < 0.01, difference between CA1 and CA3 responses to DCS.