Figure 5.
Excitatory and Inhibitory Projections from the Antennal Lobe to the MB and LH
(A) Maximum intensity projection of 119 confocal sections (1.5 μm) through the central brain of a fly carrying Mz699-GAL4:UAS-mCD8-GFP transgenes. The Mz699 enhancer element labels ∼39 ventral iPNs (D) and ∼86 cells in the vlpr (E).
(B) Maximum intensity projection of 113 confocal sections (1.5 μm) through the central brain of a fly carrying GH146-GAL4:UAS-GCaMP3 transgenes. The GH146 enhancer element labels ∼90 mostly excitatory dorsal and lateral PNs.
(C) Maximum intensity projection of 67 confocal sections (1.5 μm) through the central brain of a fly carrying Mz699-GAL4:UAS-GFPDSyd-1;UAS-DenMark transgenes. GFPDSyd-1 (magenta) labels presynaptic terminals. Fluorescence in the LH originates mainly from iPN axons, whereas signal in the vlpr arises from ipsi- and/or contralateral projections of vlpr neurons. The vlpr cells may also elaborate presynaptic sites in the LH, but these are obscured by the strong iPN signal. DenMark (cyan) labels putative dendritic regions. Although iPN dendrites are found exclusively in the antennal lobes, vlpr neurons receive their main input in the LH. Faint DenMark labeling suggests additional weak dendritic sites of vlpr cells in the vlpr. See Movie S1 for the complete image stack.
(D and E) Confocal sections through the central brain of a fly carrying Mz699-GAL4:UAS-mCD8-GFP transgenes, after immunostaining against GABA (magenta, left column) and GFP (cyan, center column); colocalization of both markers results in white structures in the overlay images on the right. In some images, nuclei are counterstained with TOTO-3 (yellow). The approximate positions of the imaged areas are indicated in (A). The images were acquired and are displayed at different photomultiplier gain and contrast settings.
(D) An individual confocal section (1 μm) shows GABAergic iPNs. See Movie S2 for the complete confocal image stack.
(E) A maximum intensity projection of 70 confocal sections (1 μm) demonstrates the absence of GABA staining in vlpr neurons. See Movie S3 for the complete confocal image stack.
(F and G) Two-photon imaging of odor-evoked calcium transients in flies carrying MZ699-GAL4:UAS-GCaMP3 transgenes.
(F) Single-trial responses of iPN axons to 5 s pulses of nine different odors (black bar). The traces, which were recorded in the same fly, are aligned to the time of odor onset and color-coded according to the number of glomeruli an odor activates.
(G) Integrated fluorescence transients (area under the fluorescence trace during a 5 s odor pulse) in iPN axons as a function of the number of glomeruli an odor activates (mean ± SEM, R2 = 0.9278, p < 0.0001, n = 11 flies per data point).
See also Figure S5 and Movies S1–S3.