Figure 7. Action potentials propagate reliably in the axonal arbor at low frequency.

Left panel, fluorescence image of an axonal branch point. Distal to an axonal branch point on both higher-order branches a bouton was selected (circles) where an AP-evoked Ca²⁺ transient was detected. Right panel, top trace shows somatic recording of APs evoked by brief current injection. At low AP frequency the fluorescence increase evoked by single APs was detectable in both boutons (lower two traces). Cell was loaded with 200 μM OGB-1.