ELECTRICAL BURSTING AND LUMINAL CALCIUM OSCILLATION IN EXCITABLE CELLMODELS

It is shown in this paper that electrical bursting and the oscillation s in the intracellular calcium concentration, [Ca2+](i), observed in e xcitable cells such as pancreatic beta-cells and R-15 cells of the mol lusk Aplysia may be driven by a slow oscillation of the calcium concen tration in the lumen of the endoplasmic reticulum, [Ca2+](1um). This h ypothesis follows from the inclusion of the dynamic changes of [Ca2+]( 1um) in the Chay bursting model. This extended model provides answers to some puzzling phenomena, such as why isolated single pancreatic p-c ells burst with a low frequency while intact p-cells in an islet burst with a much higher frequency. Verification of the model prediction th at [Ca2+](1um) is a primary oscillator which drives electrical burstin g and [Ca2+](i) oscillations in these cells awaits experimental testin g. Experiments using fluorescent dyes such as mag-fura-2-AM or aequori n could provide relevant information.