Figure 6.

Somatic action potentials elevate dendritic calcium in a manner that does not rely on dendritic sodium channels in P30–P33 SCs. A–D, As shown for a representative experiment, action potentials were evoked in the soma and the resulting calcium signals were measured at the site indicated in A (blue box). The axon has been removed for clarity. B, Membrane voltage (left) and calcium elevations following a single action potential (middle) and an action potential train (2 s, 100 Hz, right) are shown. Calcium elevations were substantially smaller compared with SCs obtained from P17–P19 rats. Somatic depolarization evoked action potentials in current clamp (B) but failed to do so in the presence of TTX (C). In the presence of TTX, the cell was then voltage clamped with the action potential waveform (D). E, Calcium elevations are summarized for dendritic sites 70–100 μm from the soma (n = 6 neurons) for single action potentials (left) and action potential trains (right).