Figure 7.

GECI responses in the adult CNS in vivo. All GECIs reproducibly exhibited fluorescence changes in the CNS of adult Drosophila flies. GECIs were expressed in a subset of large tangential neurons (and few unknown interneurons) of the optic lobe (genotype, DB331-Gal4→ UAS-GECI). Details of the preparation were given by Joesch et al. (2008). In short, a young female fly was glued to a holder and its head was bent down such that its back side faced upward. The back side of the head was opened up to expose the caudal optic lobes with GECI-expressing neurons. The preparation was covered with Ringer's solution and imaged for 33 s using wide-field epifluorescence microscopy. During the experiment, the external potassium concentration was raised to 100 mm. Fluorescence responses were recorded at somata and axons of the large tangential cells. Each data point represents the maximum fluorescence change recorded in one animal. Before calculation of the fractional fluorescence changes, motion artifacts were reduced by alignment of the sequential images. DB331-Gal4 flies were a generous gift from Reinhard Stocker, University of Fribourg, Fribourg, Switzerland.