Visualizing ATP-Containing Vesicles in Astrocytes

In cultured brainstem astrocytes, ATP-containing vesicular compartments were visualized by quinacrine staining (5 µM, 15 min incubation at 37 °C). The acridine derivative quinacrine is a weak base that binds ATP with high affinity and can be used to identify putative ATP-containing vesicles in living cells, including astrocytes^{12 (link),27 (link),40 (link)}. An Olympus TIRF microscope was used to monitor fusion events^{12 (link),40 (link)}. Fluorescence was excited at 488 nm and collected at 500–530 nm. The imaging setup included a high-numerical-aperture (NA) oil-immersion objective (×60, 1.65 NA), an inverted microscope (IX71; Olympus), and a cooled charge-coupled-device camera (Hamamatsu). Images were analyzed using Olympus Cell^tool software (Olympus). The experiments were performed at 37 °C.