Numerical study of IP₃-induced Ca²⁺ spiral pattern evolution

The effect of change in concentration of messenger molecule inositol 1,4,5-trisphosphate (IP_3) on intracellular Ca^2 + spiral pattern evolution is studied numerically. The results indicate that when the IP_3 concentration decreases from 0.27 \mu M, a physiologically reasonable value, to different values, the spiral centre drifts to the edge of the medium and disappears for a small enough IP_3 concentration. The instability of spiral pattern can be understood in terms of excitability-change controlled by the IP_3 concentration. On the other hand, when the IP_3 concentration increases from 0.27 \mu M, a homogeneous area with a high Ca^2 + concentration emerges and competes with the spiral pattern. A high enough IP_3 concentration can lead the homogeneous area to occupy the whole medium. The instability of spiral pattern is ascribed to the change in stability of a stationary state with a high Ca^2 + concentration.