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. 2017 May 3;11:30. doi: 10.3389/fncir.2017.00030

Figure 2.

Figure 2

MZ699-vPNs are the source of excitation to the ePNs. (A) Schematic illustration shows how a circular flash of 590 nm light was directed sequentially to the antennal lobe (AL), lateral horn (LH), vlpr and then back to the AL. Example traces from a VM7 ePN are shown on the right (mean ± SD). (B) All recorded ePNs showed the greatest depolarization when 590 nm spot was directed to the AL (n = 7, paired t-test, **p < 0.01). The identities of four ePNs filled with biocytin hydrazide are shown on the left. (C) Grid stimulation of areas devoid of CsChrimson expression (e.g., upper red square) induced much smaller depolarization in an ePN (mean ± SD) than stimulation of areas including the AL (e.g., lower red square). The bundle of MZ699-vPNs projecting to the LH, the MZ699-vPNs’ somata, and the vlpr neurons are indicated with a white arrow, a white arrowhead and a green arrow, respectively. The AL is encircled with a white dotted line. (D) In all six ePNs, stimulation of an area without CsChrimson expression induced smaller depolarization than stimulation of areas including the AL (**p < 0.01, paired t-test). The glomerular identities of recorded ePNs are as follows: from the ePN with the largest magnitude with stimulation of AL, VM7, VM2, VM2, DC2, DC2 and VA1d. (E1,E2) MZ699-Gal4 drove expression of CsChrimson (green) in vPNs (an axon bundle indicated with an arrow) and two fibers innervating the AL (arrowheads). (E3,E4) A genetic intersection strategy (crossing MZ699-Gal4 and Gad1-LexA::QFAD) eliminated expression of CsChrimson selectively in the vPNs while expressing CsChrimson specifically in the two fibers (arrowheads). (F) Example voltage traces from two ePNs in the same type of glomerulus (VM5d). Top: full MZ699-Gal4; Bottom: spatially restricted genotype (mean ± SD). (G) Compared to results from the full MZ699-Gal4 group, depolarization magnitude was much smaller when expression of CsChrimson in vPNs was eliminated from MZ699-Gal4 expression pattern (n = 8 for control group, n = 7,1.68 ± 0.14 mV for experimental group, ***p < 0.001, two-way analysis of variance (ANOVA)). This result shows that, of the neuron populations tested, only MZ699-vPNs provide excitation to the ePNs.