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. 2020 Feb 20;18(2):e3000361. doi: 10.1371/journal.pbio.3000361

Fig 3. RIS and PVC activate each other, forming a positive feedback loop.

Fig 3

(A–E) RIS depolarization leads to a strong PVC depolarization outside of and during lethargus. This PVC depolarization is almost abolished in flp-11(tm2706), and it is significantly reduced in AVE-ablated worms. *p < 0.05, **p < 0.01, Wilcoxon signed rank test (S1 Data, Sheets 3A, 3B, 3C-E). (F) AVE-ablated worms show increased sleep. AVA-ablated worms do not show a significant sleep phenotype. Shown are sleep fractions during lethargus. *p < 0.05, Kolmogorov-Smirnov test (S1 Data, Sheet 3F). (G) RIS does not reach the same activation levels in aptf-1(gk794) and flp-11(tm2706) mutants compared to wild-type worms. aptf-1(gk794) and flp-11(tm2706) mutants neither immobilize nor sleep during RIS activation. ***p < 0.001, Welch test (S1 Data, Sheet 3G-I). (H) flp-11(tm2706) mutants have significantly fewer wide RIS peaks. aptf-1(gk794) mutants display the same amount of wide RIS peaks as wild-type worms. **p < 0.01, Kolmogorov-Smirnov test (S1 Data, Sheet 3G-I). (I) flp-11(tm2706) and aptf-1(gk794) mutants do not show sleep during lethargus. **p < 0.01, Kolmogorov-Smirnov test (S1 Data, Sheet 3G-I). (J) A circuit model for the positive feedback loop between RIS and PVC. Activating synaptic input is shown as green arrows, inhibitory synaptic input is shown as red arrows, and gap junctions are indicated as black connections. During wakefulness, reverse command interneurons inhibit PVC so that PVC does not activate RIS. During lethargus, PVC directly activates RIS, which then inhibits reverse command interneurons through FLP-11. This may speculatively disinhibit PVC, leading to a positive feedback. ΔF/F, change of fluorescence over baseline; FLP-11, FMRF-Like Peptide 11; GCaMP, genetically encoded calcium indicator; n.s., not significant.