Figure 3. Distance-dependence of iontophoresis-evoked Ca²⁺ transients in axon varicosities.

(A₁) Stellate cell image shows the axonal recording sites for Ca²⁺ measurement and the dendritic location of the iontophoretic pipette used for NMDAR stimulation. Magnified views of axonal varicosities are shown in the boxed insets with the positions of line scans (dashed lines). (A₂) An NMDAR-mediated depolarization (V_rest= −70 mV) resulted from dendritic iontophoresis of L-aspartate. (B) Ca²⁺ transients recorded in proximal (site 1) and distal (site 2) axon varicosities evoked by dendritic iontophoresis. (C) Amplitudes of Ca²⁺ transients recorded in axon varicosities versus the distance of the recording site from the axon hillock. (D) Single exponential fits of the rising phase of Ca²⁺ transients versus distance from the axon hillock.