Figure 1. Intra-oral quinine delivery and footshock increase Ca²⁺ signals in VGlut2-expressing neurons in the LHb.

(A) Schematic of the fiber-photometry setup. We recorded Ca²⁺ transients from GCaMP6-expressing neurons from the LHb of freely behaving mice. DM, dichroic mirror; PMT, photomultiplier tube. (B and C) Injecting recombinant AAV-DIO-GCaMP6m (B) into the LHb of a Slc17a6-ires-Cre (Vglut2-LHb-GCaMP6) mouse resulted in GCaMP6m expression (green) in LHb neurons (C). Postmortem examination verified the location of the implanted optical fiber. Blue, DAPI counterstaining of cell nuclei. (D) Recording sites within the LHb (n = 9 mice). Each green dot represents the center of optical tip in an individual mouse. (E) The schematics of intra-oral solution infusion through a cheek fistula. (F) Raw trace of fluorescence changes shows that intra-oral delivery of quinine (horizontal bar) rapidly increased GCaMP6 signals within one test trial. (G and H) Trial-by-trial heatmap representation of GCaMP6m transients evoked by random quinine infusion (n = 10 trials; G) and peri-event plot of the average Ca²⁺ transient for a mouse (H). Color scale indicates the range of ΔF/F in (G); (I) Average Ca²⁺ signals associated with intra-oral quinine infusion for the entire test group (n = 7 mice). (J–N) The effects of footshock. (J) Schematics showing footshock application. (K) The raw trace shows a footshock-evoked change in GCaMP6 fluorescence within one test trial. (L) Heatmap representation of GCaMP6 signals across trials. (M) Average GCaMP6 transients across trials for the same mouse shown in (C). (N) Average GCaMP6 transients for the entire test group (n = 8 mice). In (H, I, M, and N), thick lines indicate the mean, shaded areas indicate the SEM, and the dashed lines indicate the onset of quinine infusion or footshock. Red segments indicate statistically-significant increases from the baseline (p<0.05; multivariate permutation tests).

DOI: http://dx.doi.org/10.7554/eLife.23045.002

Figure 1—figure supplement 1. Quinine and footshock do not evoke substantial changes in GFP fluorescence in the control Vglut2-LHb-EmGFP mice.

(A) Effect of intra-oral quinine infusion (dashed vertical line) on the GFP fluorescence in the LHb of Vglut2-LHb-EmGFP mice (n = 5 mice). (B) Effect of footshock on the GFP fluorescence in the LHb of control mice (n = 5 mice).

DOI: http://dx.doi.org/10.7554/eLife.23045.003