Figure 5

Relative changes in Ca²⁺ levels of each compartment during an oscillation cycle. (A,B) Normalized relative changes in [Ca²⁺] are plotted following stimulation with low [IP₃] (region α; A) and intermediate [IP₃] (region β; B) during the duration of one oscillation cycle with peaks labeled for each compartment. The µd peaked first in both regions (green line in A,B). The Cyt peaked before the Mt in region α (black and cyan lines in A), while it peaked after the Mt in region β (black and cyan lines in B). (C,D) The slopes of the curves of relative [Ca²⁺] changes for regions α and β indicate refilling or emptying of compartments as positive and negative, above or below the grey dashed line, respectively. The interspike interval of the oscillation-driving compartment is labeled (µd in region α (A,C) and Cyt in region β (B,D)). Emptying and refilling phases are also labeled (C,D), in order to show which compartment is refilling the oscillation-driving compartment during the interspike interval. The µd is refilled primarily by the Mt in region α, and the Cyt is refilled primarily by the ER in region β.