FIG. 4.

DPPX regulates the excitability of CA1 pyramidal neurons. A: traces recorded on suprathreshold, 300 pA, current injection in siDPPX (red traces) and negative control siRNA-expressing neurons (black traces). Rectangles indicate portion of the traces shown in B. B: enlarged and overlapped traces from A show siDPPX-expressing neurons (red trace) have a delayed onset and higher voltage threshold for the 1st action potential (AP) on step-current injection compared with negative control siRNA-expressing neurons (black trace). C: pooled AP onset and threshold data for siDPPX (red bars) and negative control siRNA-expressing neurons (gray bars). One day postinfection (open bars), no difference in either onset or threshold is observed between experimental groups. However, both onset and threshold are affected by siDPPX expression beginning 2 days postinfection (filled bars). Threshold data are measured from ramp current injections (Kim et al. 2005). Asterisks indicates P < 0.05. Error bars represent SE. D: broadened and aligned traces from A to show that the 1st AP initiated in siDPPX-expressing neurons (red trace) are broader with weaker afterhyperpolarization compared with negative control siRNA-expressing neurons (black trace). E: pooled AP width and afterhyperpolarization (AHP) data for siDPPX (red bars) and negative control siRNA-expressing neurons (gray bars). One day postinfection (open bars), no difference in either width or AHP is observed between experimental groups. However, both are affected by siDPPX expression beginning 2 days postinfection (filled bars). Numbers in parentheses are the “n” number for data in C and E. Asterisks indicates P < 0.05. Error bars represent SE.