Blocking synaptic glutamate release from ACs suppresses the rhythmic depolarization in <i>I</i>_h mutant photoreceptors.

Abstract

<p>(<b>A</b>) Ultrastructure of lamina cross-sections in wild-type and <i>I</i>_<i>h</i> mutant flies. The left panel shows the organization of the columnar neurons with synaptic connections in the lamina. Photoreceptor cells are shown in gray, L1–L2 neurons in black, and ACs in red. These neurons are present in all lamina columns, and single example profiles are shown arrayed across the lamina. The middle and the right panels show EM images of lamina cross-sections in wild-type and <i>I</i>_<i>h</i> mutant flies, respectively. Photoreceptor axons are colored in yellow and AC processes in blue. (<b>B</b>) Intracellular recording traces of <i>I</i>_<i>h</i> mutant flies with expression of TeTxLC using <i>L1L2-GAL4</i> and <i>Lai-GAL4</i> drivers. The fractions of photoreceptors that exhibit rhythmic depolarization are presented in the middle panel, and the time (t_3/4) required for a 3/4 recovery from the responses upon stimulation cessation is shown in the right panel. The numbers of recorded flies are listed. (<b>C</b>) Inactivation of ACs via ectopic expression of dORK^ΔC suppresses rhythmical depolarization in <i>I</i>_<i>h</i> mutant flies. The fractions of flies that exhibit ERG oscillation phenotype and the numbers of recorded flies are presented in the right panel. An ERG trace of flies expressing dORK^ΔC in wild-type ACs is also presented. (<b>D</b>) Intracellular recording traces of <i>I</i>_<i>h</i> mutant flies expressing <i>UAS-vGluT-RNAi</i> using different drivers. The fractions of photoreceptors that exhibit rhythmical depolarization are presented in the middle panel, and the time (t_3/4) required for a 3/4 recovery from the responses upon stimulation cessation are shown in the right panel. The number of recorded flies for each genotype is listed.</p