Fig. 4. Localization of transcripts involved in monoaminergic neurotransmission using in situ hybridization. Representative frontal sections showing the labelling in the head (A,C,E,G-J) or the thorax (B,D,E). In (A,C,E) the ellipsoid body is circled with a dotted line to illustrate that sections are at approximately same depth in the head. (A,B) The SerT anti-sense riboprobe labels discrete cells in the head and in the thorax. Anatomical positions of the labelled cells in (A) are consistent with the SP1 (arrows), LP1 (notched arrow), and SE2 (barbed arrow) clusters of serotonergic neurons. Cells in (B) are present in the posterior portion of the ventral ganglion (arrows). (C,D) The DAT anti-sense riboprobe labels discrete cells in the head (C) and thorax (D). The anatomical position of the labelled cells suggests these cells are part of the DM (arrows), DL₁ (white arrowheads), and DL2 (carrot) clusters of neurons. The cells in (D) are present in the posterior portion of the ventral ganglion, and are likely to be part of the dorsal lateral cluster (barbed arrow) and the medial cluster (arrows). (E,F) The riboprobe for CG33528 labels many cells (markers have remained consistent with A and C) throughout the head (E) and thorax (F) that are in similar anatomical locations as cells that label for the transporters, SerT and DAT. Gray open arrows denote labelling of the medullary layer (MC cells). (G) Wider view of CG33528 labelling showing the cells of the brain that are labelled (arrows, barbed arrows and white arrowheads) and that a layer of cells at the base of the photoreceptors is also labelled (black arrowheads). Box denotes area of higher magnification in (H,I). (H,I) Serially sectioned preparation illustrating the region boxed in G but in a different preparation. (H) Section labelled with CG33528 shows label right at the base of the photoreceptors (PR). Block arrows denote examples where the CG33528 label has penetrated the photoreceptor layer. The dotted line represents the outline of the lamina neuropil (LaN). (I, top) Fluorescence image showing NrxIV antibody labelling glial septate junctions at the base of the photoreceptors in the same anatomical position as the CG33528 label in (H). (I, bottom) For clarity, the brightfield image of the fluorescence image has been presented so that the morphological features (i.e. the characteristic striations of both the photoreceptor layer and the lamina neuropil) that define the different layers in optic lobes can be distinguished. The broken line outlines the lamina neuropil and the solid line denotes the base of the photoreceptors. (J) The riboprobe for the histamine synthesizing enzyme, histidine decarboxylase (HDC), labels cells in the central brain region (arrows) as well as the photoreceptor cell bodies (barbed arrows). In all panels dorsal is up. Scale bars, 50 µm.