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.