Figure 4. The Aedes CO₂ receptor is inhibited by isobutyric acid only when Gr1 is present.

(A) Representative traces of a cpA neuron in female Aedes aegypti responding to CO₂ overlaid with isobutyric acid, and (B) mean percent inhibition of cpA responses by odorants relative to solvent. Odorants were diluted at 10% (v/v) in paraffin oil and presented as a 0.5 s stimulus during a 2 s pulse of 0.1% CO₂ (n = 5–6). Error bars are s.e.m. (C) Representative traces of a CO₂ empty neuron expressing mosquito Grs in D. melanogaster responding to a 2 s pulse of CO₂ overlaid with 0.5 s of isobutyric acid or solvent. Dots mark action potentials attributed to the ab1C neuron during part of the baseline and the 0.5 s stimulus window. (D) Mean response of the transgenic ab1C neuron to inhibitor overlay in flies expressing combinations of mosquito Grs (n = 6–9; t-test, **p < 0.01, ***p < 0.001). Odorants were diluted at 1% (v/v) in water and presented as a 0.5 s stimulus during a 2 s pulse of 0.7% CO₂. Error bars are s.e.m. (E) Model of receptor subunit contributions to odorant response.