Temporal staining pattern of another BG transgenic strain. Males from the BG6 line (see Materials and Methods) for which the genetic backgrounds were either per⁺ orper⁰¹ were sectioned and stained with anti-β-GAL. In per⁺, only weak staining of the LN_v (arrow) and PRs was observed at ZT9. Staining in glia was nearly undetectable at this time point. At ZT21, strong staining in the LN_v(arrow) and PRs, as well as weak staining in glia (in the lamina and bordering the medulla), can be observed. Inper⁰¹, only light staining of the LN_v is observed at ZT9 (arrow). In contrast to the expression of BG6 in theper⁺ background, there is also prominent staining in the nuclei of the PRs and glia cells (arrowhead). At ZT21, LN_v are strongly labeled, whereas the signal intensities in the PRs and glia seem to be only slightly stronger compared with ZT9. Scale bar, 25 μm.