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. 2022 Apr 20;13:855522. doi: 10.3389/fphys.2022.855522

FIGURE 6.

FIGURE 6

Two-order olfactory projection patterns underlying vomiting signaling in the brain. (A,B) Confocal images of the brain (A) and the SOG (B) with stained afferents originating from the maxillary palp. (A′,A′′) Three-dimensional reconstruction of the stained neurons shown in (A) (frontal and lateral views, respectively). (B′) Three-dimensional reconstruction of the stained neurons shown in (B). (C-C′′) Terminals of sensory neuron axons originating from the maxillary palp innervate the AMMC (C), the LG (C′), and the CRE (C′′). (D,D′) Confocal images of the brain with stained afferents originating from pb3. The dotted box in (D) marks two plexi of axons originating from the pb3 neurons running through the ipsilateral TC. The dotted line marks the projected region in the brain, and the white arrow shows the axonal entry point into the LG. (D′′) Three-dimensional reconstructed images of the ORN axons shown in (D). (E,E′) Confocal images of the brain with stained afferents originating from pb1. The projected region is marked by the dotted line. The white arrow in (E) shows the axonal entry point into the LG, and the white arrows in (E′) show four branches of the axons in the LG. (E′′) Three-dimensional reconstructed images of the ORN axons shown in (E). (F) Confocal images of the main glomerular lobe-calycal pathway obtained by selective staining of PNs linked to the LG. The LG is specifically connected to the ACA of the MB. (F′,F′′) Three-dimensional reconstruction showing the overall projection pathway of the PNs in the LG (frontal and lateral views, respectively). The dotted line marks the soma clusters of the PNs. (G) Schematic representation of the neural circuit of locust vomiting. SOG, suboesophageal ganglion; CC, circumoesophageal connective; TC, tritocerebrum; DC, deutocerebrum; PC, protocerebrum; AL, antennal lobe; LG, lobus glomerulatus; CRE, crepine; AMMC, antennal mechanosensory and motor center; MB, mushroom body; CA, calyx; ACA, accessory calyx; PED, pedunculus; A, anterior; D, dorsal; M, medial; P, posterior; and V, ventral. Scale bars: 200 µm in (A-A′′), (B-B′′), (D-D′), (E-E′), and (F-F′′); 100 µm in (C-C′′) and the dotted box of (D); and 50 µm in (D′′) and (E′′).