Fig. 6: Aion enables inhibition of nociceptive circuit function in Drosophila melanogaster larvae over extended time periods.

a Schematic model of nociceptive sensory neurons (C4da) and connected downstream neurons (A08n) in Drosophila larvae. The example image shows Aion expression in A08n neurons (green, maximum intensity projection of confocal image stack). Fas3 staining (magenta) was used as a sensory axon marker for orientation. Arrows indicate cell bodies of A08n neurons. Scale bar: 20 µm. b Nociceptive touch responses were strongly reduced after blue light in animals expressing Aion in A08n neurons, but not in controls (wt). The responses could be fully recovered after orange light exposure. c Larvae expressing GtACR1 in A08n neurons showed robustly reduced nociceptive responses under constant green light exposure. d Constitutive silencing by expression of Kir2.1 in A08n neurons leads to similarly strong inhibition of larval nociception as with Aion. For b–d the behavioral response to a 50 mN mechanical stimulus is shown. e All-optical paradigm for inhibition of A08n neurons with Aion and activation of C4da neurons with CsChrimson. Repeated induction of nociceptive behavior with red light was strongly inhibited after blue light-induced Aion activation and largely reversed by orange light. f Activation of Aion expressed in A08n neurons with a single blue light pulse (5 s) resulted in reduction of nociceptive responses for at least 15 min and partially recovered only after 60 min. For e, f behavioral responses to CsChrimson activation in C4da neurons at the indicated time points are shown. Χ²-test, n of animals are indicated by white numbers in b–f. For clarity, only significant differences are indicated. *p < 0.05, **p < 0.01, ***p < 0.001 For further details on statistics see Supplementary Data 1.