Figure 4.

Caffeine-induced changes in whole-cell currents of ARPE-19 cells. To monitor changes in whole-cell currents the following pulse protocol has been used: every 2.5 s the cells were hyperpolarized from a holding potential of −70 mV to five potentials with 20 mV increment for 100 ms. These hyperpolarizations were followed by five depolarizing voltage steps with 20 mV increment for 100 ms. Caffeine led to a strong down-regulation of outward currents in ARPE-19 cells. At the bottom typical current responses before (‘control’), during (‘caffeine’) and after (‘wash-out’) application of 50 mM caffeine are shown.