Figure 1. Development of I_CRAC following store depletion.

A, the upper panel shows the typical voltage ramp protocol used to monitor I_CRAC in mast cells, the related rat basophilic leukaemia (RBL-1) cell line and jurkat T-lymphocytes. The ramp spans −100 to +100 mV in 50 ms, and is applied from a holding potential of 0 mV once every 2 s. The lower panel depicts the time course of activation of I_CRAC. The current amplitude, measured at −80 mV from each ramp, has been normalised for cell size by dividing the current by cell capacitance. The thick line shows a mono-exponential fit to the activation time course. B shows the current-voltage relationship, once the current had reached steady state. Note the inward rectification and very positive reversal potential, characteristic of I_CRAC. The pipette solution is caesium glutamate based, supplemented with InsP₃ and 10 mm EGTA.