Figure 2. Distinct interneurons act in opposition to regulate CO₂ avoidance in animals raised at ambient CO₂.

(A-B) In animals raised at ambient CO₂, silencing of AIZ and ablation of AIY enhances CO₂ avoidance, ablation of RIG reduces CO₂ avoidance, and ablation of RIA results in CO₂ attraction. Animals were raised at ambient CO₂ and screened for responses to 1% CO₂ (A) and 10% CO₂

(B). Interneurons were either genetically ablated individually (AIB-, AIY-, RIA-, RIB-, and RIG-); genetically ablated simultaneously (AVA- AVE- AVD-); or silenced with tetanus toxin simultaneously (AIB- AIZ-). *p<0.05, **p<0.01, ***p<0.001, one-way ANOVA with Dunnett’s post­test (A) or Kruskal-Wallis test with Dunn’s post-test (B). n=8–26 trials per genotype and condition.

(C) Ablation of AIY enhances CO₂ avoidance. By contrast, animals with more active AIY neurons due to AIY-specific expression of pkc-1(gf) show reduced CO₂ avoidance. Animals were raised at ambient CO₂. ***p<0.001, two-way ANOVA with Dunnett’s post-test. n=8–26 trials per genotype and condition.

(D) Ablation of RIG reduces CO₂ avoidance. By contrast, animals with more active RIG neurons due to RIG-specific expression of pkc-1(gf) show enhanced CO₂ avoidance. Animals were raised at ambient CO₂. *p<0.05, **p<0.01, two-way ANOVA with Dunnett’s post-test. n=8–30 trials per genotype and condition.

(E) Ablation of RIA reduces CO₂ avoidance. By contrast, animals with more active RIA neurons due to RIA-specific expression of pkc-1(gf) show enhanced CO₂ avoidance. Animals were raised at ambient CO₂. *p<0.05, **p<0.01, ***p<0.001, two-way ANOVA with Dunnett’s post-test. n=8–16 trials per genotype and condition.

(F) Silencing of AIZ enhances CO₂ avoidance. Animals were raised at ambient CO₂. ***p<0.001, two-way ANOVA with Sidak’s post-test. n=8–16 trials per genotype and condition.

(G) Animals with AIY neurons transiently silenced by expression of the histamine-gated chloride channel HisCl1 in AIY show enhanced CO₂ avoidance. By contrast, animals with RIA neurons transiently silenced using the same approach show CO₂ attraction. Responses to 1% CO₂ were tested for wild-type animals and animals expressing HisCl1 in either AIY or RIA without histamine (negative control) and with histamine (neuronal silencing); changes in CO₂ response were observed only in the presence of histamine. Animals were raised at ambient CO₂. *p<0.05, ***p<0.001, Kruskal-Wallis test with Dunn’s post-test. n=8–12 trials per genotype and condition.

For A-G, graphs show medians and interquartile ranges. See also Figure S3.