Photostimulation of two types of Ca2+ waves in rat pheochromocytorna PC12 cells by ultrashort pulsed near-infrared laser irradiation

We show that focused laser irradiation can generate Ca2+ waves in differentiated PC12 cells, using highly penetrating and locally acting near-infrared ferraosecond pulsed laser light. Similar to photolytic uncaging experiments, intracellular Ca2+ concentrations could be elevated to produce a whole cell Ca2+ rise, but without the requirement for caged Ca2+. Irradiation of subcelhilar volumes in the soma or in PC12 neurites, generated a relatively slow calcium rise (speed similar to 20 mu m/s). Less frequently, a fast calcium rise (speed > 1200 mu m/s) was observed, consistent with laser-induced membrane depolarization. The probability of Ca2+ generation increased with laser power and was found to be the same in excitable (PC12) and nonexcitable (HeLa) cells.