Figure 3.

Local, Activity-Dependent Ca²⁺ Influx at Nodes of Ranvier

(A) Two-photon image of cerebellar Purkinje cell indicating line scan locations.

(B) Ca²⁺ transients (top, line scans) at locations shown in (A) during current-evoked spike trains (bottom). AIS, axon initial segment. BP1 and BP2, first and second axonal branchpoint.

(C) Frame-scan time series of BP1 during spike train. Green, axon morphology.

(D) Spike train-evoked ΔF/F at ROIs shown in (C) (red boxes). Normalized integrated ΔF/F (ΔF/F^∗s) against distance from an axonal branchpoint (bottom, n = 13 neurons).

(E) Soma, AIS, and first BP ΔF/F in response to 500-ms somatic voltage steps (voltage clamp) in bath-applied TTX (0.5 μM).

(F) Pooled data for max ΔF/F versus somatic command potential (soma, black; AIS, red; BP1, blue. n = 6 neurons).

(G) Activity-dependent changes in ΔF/F upon somatic current injection. Baseline holding current: 0 pA.

(H) Summary data for the change in ΔF/F^∗s during silence and activity (n = 5 cells).

(I) Ca²⁺ influx at the axon initial segment, first branchpoint and presynaptic boutons before and after bath application of 0 mM extracellular Ca²⁺ (n = 4), Agatoxin (AgaTX, n = 4, AIS = 3), and Mibefradil (Mibef, n = 9).

Error bars, ±SEM.