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Fig. 4
Hindbrain Inhibitory Interneurons Mediate Dopaminergic Control
(A)Confocal images from a 6 dpf Tg(GlyT2:GFP) larva showing the distribution of glycinergic interneurons around MCs in the hindbrain. The numbers “1,” “2,” and “3” indicate the location of glycinergic interneuron groups analyzed in (B)–(D). C, caudal; L, left; Ri, right, Ro, rostral. Each image shown is from one optical slice.
(B) 3D plot of the distribution of glycinergic interneurons, which exhibited spatial location-dependent functional properties. The frequencies of spontaneous and flash-evoked spiking activities are color- and symbol size-coded, respectively. Filled circles represent neurons irresponsive to flash stimuli. The three groups were roughly classified based on the spatial location and functional properties. The thick gray lines outline the MC morphology.
(C) Sample traces showing spontaneous firing activities of the three groups of glycinergic interneurons.
(D) Summary of 15 ms flash-evoked firing responses of the three groups of glycinergic interneurons.
(E) Schematic of two-photon lesion of glycinergic interneurons and in vivo whole-cell recording of bilateral MCs. +, intact side; - , lesion side.
(F-H) Effects of the lesion of the group 1, 2, 3, or both 2 and 3 on the total integrated charge (F), duration (G), and amplitude (H) of MC CSCs evoked by 15 ms flash stimuli.
(I) Effect of the lesion of both contralateral group 2 and ipsilateral group 3 on the total integrated charge of expanding stimulus-evoked MC CSCs.
(J-O) Retrograde tracing of glycinergic interneurons and optic tectal neurons by local injection of neurobiotin (NB) at the vicinity of MC ventral dendrites in a 6 dpf Tg(GlyT2:GFP) larva.
(J) Schematic of the locations of injection and imaging.
(K) Injection site (ellipse) at the right hindbrain. Arrowheads indicate non-specific signals on the skin.
(L) Schematic showing the location of images in (M)-(O). Single optic slices from different layers of the outlined areas are enlarged in (M)-(O).
(M) NB-positive neurons in the ipsilateral optic tectum.
(N) NB-positive glycinergic interneurons in the contralateral (“Left”), but not ipsilateral (“Right”), group 2. Asterisks indicate both NB- and GFP-positive cells. Based on z stack images, there were 6 NB-positive cells in the left brain, and 4 of them were also GFP-positive, whereas there were 3 NB-positive cells in the right, and none of them were co-labeled by GFP.
(O) NB-positive glycinergic interneurons in the ipsilateral (right side), but not contralateral (left side), group 3. Asterisks indicate both NB- and GFP-positive cells. Based on z stack images, there were 4 NB-positive cells in the left, and none of them were co-labeled by GFP, whereas there were 13 NB-positive cells in the right, and 10 of them were also GFP positive.
n.s., not significant; p < 0.05, p < 0.01, p < 0.001; error bars, SEM.
See also Figures S4 and S5.