Fig. 2.

Cathodal and not anodal direct current stimulation (DCS) significantly inhibits field excitatory postsynaptic potentials (fEPSPs) in the basal dendrites of CA1 neurons evoked by stimulation of association fibers in stratum oriens. A, C, and E: representative fEPSP recordings (averages of 7 consecutive traces) before (left), during (middle), and after (right) DCS at 100, 200, and 400 μA, respectively. DCS polarity was defined as the polarity of white DCS electrode relatively to gray electrode as shown in Fig. 1. The scaling bars correspond to 500 μV and 10 ms. B, D, and F: time courses of average values normalized to the baseline fEPSP slopes. DCS starts at time 0 and ends after 5 min as shown by the filled bars. Open circles correspond to positive (anodal) DCS, and filled circles correspond to negative (cathodal) DCS. Numbers of slices per experiment are equal to 4, 6, 6, 7, and 8 for −400, −200, −100, +100, and +200 μA of DCS, respectively. Error bars correspond to SE.