Figure 6.

Drosophila melanogaster: a subpopulation of GABAergic neurons are co-stained with anti-OA1 antibodies. (A) Schematic of the organization of the Drosophila olfactory system in sagittal view. MP, maxillary palp; ORN, olfactory receptor neuron; SEG, subesophageal ganglion; ant lob, antennal lobe; ca, calyx, ped, pedunculus; v, vertical lobe of MB; A, anterior; P, posterior; Dorsal, Ve- ventral. Broken lines indicate the approximate orientation of sections through antennal lobe (in C,F,D) and lateral protocerbrum (E). (B) Section through the center of one glomerulus labeled with anti-synapsin (green, B1) and anti-GFP in ORNs (magenta, B2) in OR83b-GAL4;UAS-mcd8-GFP flies. The glomerulus has a core area where the ORNs do not branch (B3). (C1) Anti-OA1 stained groups of cells and processes in the glomeruli and the aglomerular neuropile area of the antennal lobe in OR83b-GAL4;UAS-mcd8-GFP (C1, magenta) on the oblique frontal brain cross-section of the antennal lobe. (C2) In the same section, GFP (green) takes up a large percentage, or perhaps all, of the olfactory receptor endings in the antennal lobe glomeruli. (C3) The majority of the sensory neurons terminals do not label with the OA1 antiserum (magenta) with a few exceptions. (D,E) Anti-OA1 antibodies do not label the majority of uniglomerular projection neurons (uPNs). (D1) Here, anti-OA1 labeled clusters of cells surrounding the antennal lobes. These neurons are not projection neurons. GH146-GAL4; UAS-mcd8-GFP projection neurons expressed GFP (green) (D2). In GFP expressing neurons there is no OA1 immunoreactivity as shown in our merged image (D3), co-localization would show as white. (E) Anti-OA1 staining is absent in most uPN axons that leave the antennal lobe via the m-APT and branch in the calyx (ca) of the MB and lateral horn (LH); one exception is the axon shown by two arrowheads (E1). mPNs leave the antennal lobe via the ml-APT, a large portion of the ml-APT fibers are OA1 positive (arrow) in (E1,E3). These fibers also exhibit anti-GABA staining (inserts in E1). Three neurons that have their axons in ml-APT are also labeled with anti-GFP and GABA in GH146-GAL4; UAS-mcd8-GFP (E2 and insert in E2). These neurons are not labeled with anti-OA1 in this brain preparation (E3). (F1) In the same section as shown in (C) anti-OA1 (magenta) labels the cell bodies of laterally located neurons. The scattered, stained processes are in all glomeruli. (F2) The same sections labeled with anti-GABA antibodies; and GABA-like immunoreactivity is found in neurons with cell bodies in lateral and dorso-lateral clusters. These neurons supply GABAergic processes to the glomeruli. The merged image (F3) of the same sections shows the group of GABAergic neurons co-stained with anti-OA1 (white). Anti-OA1 staining is found in the cell bodies and processes in the glomeruli and in the aglomerular area of the antennal lobe. Arrows in (C1) and (D1,F1) indicate lateral neurons cluster (LN) and ventral cluster (VN) of anti-AmOA1 positives neurons. In (D2), the arrowhead indicates thick fibers of the PNs entering the glomerulus that might correspond to the core area of the glomerulus. Scale bar: A = 10 μm, B–F = 20 μm.