Action potential duration is increased in CA1 pyramidal cells of <i>Fmr1</i> KO mice.

<p>(A) Single action potential in a WT and a <i>Fmr1</i> KO cell generated by a short pulse (100 μs) with an intensity that was adjusted to the spike voltage threshold. The recordings also depict the half-width (dashed line) of the spike for the measurement of action potential duration. St indicates the onset of the stimulus. (B) Train of action potentials (8–12 spikes) produced by applying 500 ms current injections at 200 pA in a WT cell and at 100 pA in a <i>Fmr1</i> KO cell. The durations of the first spike (▼), the spike in the middle of the train (250 ms after stimulus onset; ■) and the last spike of the train (●) were measured in both cell groups. (C) Histogram showing action potential duration evoked in a single action potential and in trains of action potentials in WT and <i>Fmr1</i> KO cell groups. Calibrations as indicated. Asterisks (*) indicate statistically significant differences (P<0.05).