Caffeine-induced Ca2+ oscillations in type I horizontal cell of carp retina: A mathematical model

Oscillations in intracellular free Ca²⁺ concentration ([Ca²⁺]_i) have been observed in a variety of cell types. In the present study, we constructed a mathematical model to simulate the caffeine-induced [Ca²⁺]_i oscillations based on experimental data obtained from isolated type I horizontal cell of carp retina. The results of model analysis confirm the notion that the caffeine-induced [Ca²⁺]_i oscillations involve a number of cytoplasmic and endoplasmic Ca²⁺ processes that interact with each other. Using this model, we evaluated the importance of store-operated channel (SOC) in caffeine-induced [Ca²⁺]_i oscillations. The model suggests that store-operated Ca²⁺ entry (SOCE) is elicited upon depletion of the endoplasmic reticulum (ER). When the SOC conductance is set to 0, caffeine-induced [Ca²⁺]_i oscillations are abolished, which agrees with the experimental observation that [Ca²⁺]_i oscillations were abolished when SOC was blocked pharmacologically, verifying that SOC is necessary for sustained [Ca²⁺]_i oscillations.