Fig. 1
Indole inhibits OR8-Orco activation by (R)-1-octen-3-ol. a (R)-1-octen-3-ol is an alkenyl alcohol and a potent ligand of OR8. Indole is an aromatic bicyclic organic compound. DEET is a benzyl-ester sharing a benzene ring and a nitrogen atom with indole (red features). b Representative current traces of AaegOR8-Orco activation by 10–7 M (R)-1-octen-3-ol (black arrowheads) or by a mixture of 10–3 M indole (red arrowhead) and 10–7 M (R)-1-octen-3-ol (black arrowhead). Normalized responses of AaegOR8-Orco to 10−7 M (R)-1-octen-3-ol alone (control) or in combination with 10−3 M indole (indole). Statistical significance was determined using the Wilcoxon–Mann–Whitney test (n = 5–6). Orco-injected oocytes responded to 10–3 M of the Orco agonist VUAA1 (positive control) but not to 10–3 M indole (n = 4). c Representative current traces of AaegOR8-Orco activation by (R)-1-octen-3-ol alone or in the presence of 10–4 M, 10–3 M or 10–2 M indole. Arrowheads above the traces indicate the onset of the odorant stimulus, black arrowheads represent (R)-1-octen-3-ol and red arrowheads represent indole. d Concentration–response relationships of AaegOR8-Orco in response to increasing indole concentrations. Current amplitudes were normalized to the maximum response. Statistical significance was determined using a one-way analysis of variance (ANOVA; P = 0.0142) followed by a Dunn’s multiple comparisons test (n = 4–7). e Non-normalized concentration-current response relationships (n = 4–7). f Histogram of the depolarization current response amplitudes of AaegOR8-Orco in response to (R)-1-octen-3-ol alone (black) or in combination with various indole concentrations (shades of red). Statistical significance was determined using the multiple t-test and by the Holm-Sidak method (*P ≤ 0.05; **P ≤ 0.01; ***P ≤ 0.001; n = 3–7). g Concentration–response relationships of indole-induced hyperpolarization currents exhibited by AaegOR8-Orco-injected oocytes. AaegOR8-Orco, Aedes aegypti odorant receptor 8-odorant coreceptor; DEET, N,N-Diethyl-meta-toluamide