(A) T-maze response to 1% CO2 of 21G11-GAL4 and 23C09-GAL4 flies driving UAS-Kir2.1, TubGAL80TS expression. (A and C) Black dots, no heat induction of Kir2.1 expression (see Materials and Methods). Gray dots, heat induction of Kir2.1 expression before test. The top and bottom lines represent the first and the third quartiles. The line across the box is the median. (B and C) T-maze response to three CO2 concentrations—0.5%, 1%, and 2%—of the flies with 21G11-LexA driving LexAopKir2.1 expression (B) and 23C09∩VGlut driving UAS-Kir2.1,TubGAL80TS expression (C). For 21G11-LexA driving LexAopkir2.1 expression, black dots represent parental controls, and gray dots represent constitutive Kir2.1 expression. For 23C09∩VGlut driving UAS-Kir2.1, TubGAL80TS expression, black dots represent no heat induction of Kir2.1 expression, and gray dots represent both parental controls and heat induction of Kir2.1 expression before test. Post hoc two-way ANOVA showed no significance when comparing among expressions for both control and test samples. (D) Brain and LH UAS-mCD8-GFP expression of 21G11-GAL4 and 21G11-LexA. (E) Brain and LH UAS-mCD8-GFP expression of 23C09-GAL4 and 23C09∩VGlut. (D–E) Circle highlights the LH, and oval highlights the SIP. (F and G) Dscam17.1-GFP and syt-HA expression in the LH and SIP of 21G11-GAL4 (green). In (F), circle highlights the LH. In (G), the vertical lobe of the MB is drawn to facilitate visualization of the adjacent SIP. (H) LH showing expression of 21G11-LexA (green) and the VPN lines 53A05-GAL4 (red) and 41C05-GAL4 (red). Circle highlights the LH. (I) LH expression of 23C09∩VGlut (blue circles) and the VPN lines 53A05-GAL4 (yellow line) and 41C05-GAL4 (yellow line). White circle highlights the LH. For all images, the brain neuropil was stained with nc82 (magenta and blue). ±SEM ****p < 0.0001. All p values are calculated with one-way ANOVA. d, dorsal; Dscam17.1, Down syndrome cell adhesion molecule with isoform 1 of the transmembrane domain; l, lateral; LH, lateral horn; m, medial; MB, mushroom body; nc82, monoclonal antibody to Bruchpilot; PN, projection neuron; SEM, standard error of the mean; SIP, superior intermediate protocerebrum; v, ventral; VPN, V-glomerulus–innervating PN.