VU0183254 antagonizes odor-evoked ORN activity <i>in vivo</i>.

<p><b>A.</b> Representative traces of Cp neuron activity in response to a 1 s pulse of 1-octen-3-ol (dark bar above traces). Vertical lines under each raw trace indicates spike counter for CpB and CpC spikes only. Vehicle-only trace (top) responds strongly to 1-octen-3-ol, while preparations exposed to VU0183254 (bottom) do not respond. <b>B.</b> Quantification of traces as in (A). Spike frequencies were binned every second for 5 seconds prior to 1-octen-3-ol pulse and for 2 seconds afterwards. In the presence of vehicle alone (blue circles, n = 11) CpB/C neurons respond to a 1 s pulse of 1-octen-3-ol with increased activity, while preparations including VU0183254 (red squares)(n = 11) do not respond as strongly (*, p<0.05; **, p<0.005).</p

VU0183254 is an allosteric antagonist.

<p><b>A.</b> Concentration response curves of AgOrco+AgOr65 expressing HEK cells in the presence of a series of steady concentrations (expressed as logM) of pre-loaded VU0183254 (different colored lines, see inset) followed by increasing concentrations of eugenol as measured using Fluo-4AM and an FDSS6000. <b>B.</b> As in A with VUAA1. <b>C.</b> As in A, with AgOrco+AgOr48 and delta-undecalactone. <b>D.</b> As in C with VUAA1. In all cases results are shown as means+/−SEM, n = 4.</p

VU0183254 reduces Orco-mediated activity <i>in vivo.</i>

<p><b>A.</b> Representative traces of Cp neuron activity in response to vehicle (DMSO) or VU0183254 as measured by single-sensillum electrophysiology. Activity was allowed to stabilize for 10 seconds and then recorded for 60 seconds. CpA spikes can be distinguished by their larger amplitude in expansions (right panel). CpB/C spikes (counts below traces) are reduced in the presence of VU0183254. <b>B.</b> Spontaneous CpA spike rates are unaffected by the presence of VU0183254 (n = 8). Spikes were counted for each of the first 10 seconds and then averaged across the remaining 10-second intervals. Normal CpA activity is confirmed by CO₂ pulse delivered at the end of the recording period. <b>C.</b> Spontaneous firing rates of CpB/C neurons are reduced by VU0183254 in a dose-dependent manner (n = 8). All spikes were distinguished and quantified using AutoSpike software (Syntech).</p

Structure–Activity Relationship of a Broad-Spectrum Insect Odorant Receptor Agonist

Agonism of insect odorant receptor (OR) cation channels may represent a new strategy for the manipulation of destructive insect olfactory-driven behaviors. We have explored the chemical space around VUAA1, the first in class agonist of the obligate OR co-receptor ion channel (Orco), and describe novel compound analogues with increased potency across insect taxa. Functional analyses reveal several of these VUAA1 structural analogues display significantly greater potency as compared to the activity of the previously described active compounds in mobility-based behavioral assays on mosquito larvae

VU0183254 reduces OR-mediated currents.

<p><b>A</b>–<b>B</b>. Whole-cell patch clamp recordings of odorant- and VUAA1-induced currents in AgOr-expressing cells (n = 3). <b>A.</b> VU0183254 (100 µM) decreased responses to delta-undecalactone (1 µM) and VUAA1 (100 µM) in HEK cells expressing AgOrco+AgOr48. <b>B.</b> Responses to eugenol (1 µM) and VUAA1 (100 µM) in AgOrco+AgOr65 cells were reduced by VU0183254 (100 µM). <b>C</b>–<b>D</b>. Cells expressing Orco from either <i>An. gambiae</i> (<b>C</b>) or <i>Harpegnathos saltator</i> (<b>D</b>) had reduced VUAA1 (100 µM) currents in the presence of 100 µM VU0183254. <b>E.</b> Capsaicin (10 µM) currents in HEK cells expressing rat TRPVI were not reduced with by 100 µM VU0183254. Holding potential for all figures is −60 mV.</p