Sodium dependent action potentials backpropagate into the dendrites of hippocampal CA3 pyramidal neurons

In hippocampal CA1 pyramidal neurons, sodium dependent action potentials initiate near the soma backpropagate into the dendrites in an activity‐dependent manner, but they do decrease in amplitude and fail with trains of action potentials (Kano, 2000). To test the hypothesis that sodium dependent action potentials backpropagate into dendrites of CA3 pyramidal neurons, we injected a depolarizing current step somatically, in the whole‐cell patch configuration, to elicit an action potential and using calcium fluorescence as an indicator for dendritic action potentials. We measured changes in fluorescence along the somatodendritic axis and found that sodium‐dependent action potentials tend to fail to propagate at the same size within ~100 μm from the soma. These data suggest that backpropagating action potentials attenuate with distance from the soma in hippocampal CA3 pyramidal neurons.