After dissecting brains from the GAL4 driver line SS56699 with GFP staining and finding no fluorescence, I dissected them again and the immunohistochemical staining showed fluorescence. To check that the correct neurons were stained, I compared the images with the image in the paper by Hulse et al (2021; https://doi.org/10.7554/eLife.66039) . The three PPL1 dopaminergic dorsal fan-shaped body tangential neurons per hemisphere are stained, but there are some additional unidentified neurons (presumably PPM1 neruons) visible.

Hulse, B. K., Haberkern, H., Franconville, R., Turner-Evans, D., Takemura, S.-y., Wolff, T., Noorman, M., Dreher, M., Dan, C., Parekh, R., Hermundstad, A. M., Rubin, G. M., & Jayaraman, V. (2021). A connectome of the Drosophila central complex reveals network motifs suitable for flexible navigation and context-dependent action selection. eLife, 10, e66039. https://doi.org/10.7554/eLife.66039