Figure 8.

Blockade of global synaptic activity results in longer, more motile filopodia. A, Dendritic shaft from a control neuron at P3 in control ACSF (2 mm CaCl₂). The left, middle, and right panels in each row show representative snapshots of dendritic filopodia in the beginning, middle, and end of the 10-min movies. Scale bar, 5 μm (for all panels). A′, Same dendritic shaft segment ∼7 min after continuous bath application of 1 μm TTX. Note the dramatic elongation of many filopodia in three different frames of a 10-min time-lapse movie. B, Dendritic growth cone from a control neuron at P4 in control ACSF (2 mm CaCl₂). B′, Same dendritic growth cone ∼30 min after continuous bath application of TTX. Note that there is no change in the density or length of growth cone filopodia. C, Dendritic growth cone from a control neuron at P3 in control ACSF (2 mm CaCl₂). See movie 8 in supplementary data, available at www.jneurosci.org. C′, Same dendritic growth cone ∼25 min after washing in zero-calcium ACSF. Note the dramatic elongation of many filopodia in three different frames of a 10-min time-lapse movie. This effect was reversible because filopodia lengths and motility recovered after washout. See movie 9 in supplementary data, available at www.jneurosci.org.