Figure 7.

Effect of CaM dislocation on short-term facilitation during physiological patterns of AP firing. (A) Comparison of Ca²⁺ dynamics and vesicular release probability p_v at a representative coupling distance d = 40 nm for the case of Ca²⁺-dependent CaM dislocation (left) and for the control case of irreversible membrane bound CaM (right). Top, physiological AP stimulus pattern; middle, [Ca²⁺] time courses; bottom, p_v plots. (B) Snapshots of spatial distribution of normalized local total [CaM]^local_tot (which accounts for all CaM molecules in a given voxel, irrespective of their Ca²⁺ binding state) in the AZ, illustrating progressive dislocation of CaM from the AZ during the burst of APs [the same stimulation pattern as in (A)]. Scale bar 100 nm. (C) Dependency of normalized [CaM]^local_tot after the burst of APs on the coupling distance d. Normalized [CaM]^local_tot in (B) and (C) were calculated by dividing the spatially dependent [CaM]^local_tot by the initial total [CaM]_tot = 1023 μM. (D) Dependences of post-AP burst PPR_pv on the coupling distance d calculated for the single AP at t = 400 ms and for the first AP in the burst.