Excitatory responses from an ORN housed in the maxillary palp basiconic sensillum pb1A when challenged with three insect repellents: DEET, IR3535 and picaridin.

<p>Two types of neurons, A and B, are identified on the basis of their spike amplitudes. The ORN with larger amplitude, A, is stimulated by the three insect repellents, whereas the neuron with smaller amplitude, B, was unresponsive. Source dose, 100 µg.</p

Repellency assay indicating avoidance of <i>D. melanogaster</i> to three insect repellents: DEET, IR3535, and picaridin.

<p>(<i>A</i>) Male and female flies responded equally to DEET (<i>N</i> = 180 flies tested). Female flies avoid entering the food chambers treated with (B) IR3535 (<i>N</i> = 90 flies tested) and (C) picaridin (<i>N</i> = 90 flies tested). Data are from 9 independent trials for each test, with ten flies used in each trial.</p

Dose-dependent excitatory responses from a picaridin-sensitive ORN housed in an antennal basiconic sensillum ab3 on <i>D. melanogaster</i> antennae.

<p>Hexane (control) responses were subtracted. (<i>N</i> = 7). Error bars are standard error of the mean (SEM).</p

Dose-dependent responses from ab3A neuron of transgenic flies expressing Or42a (w; Δhalo; UAS-DmOr42a/Or22a-GAL4).

<p>Test flies were challenged with DEET, IR3535, and picaridin (<i>N</i> = 15). Error bars are standard error of the mean (SEM).</p

Action potentials recorded from ab3 sensilla.

<p>Δhalo flies showed spontaneous activity of neuron B, but not A, thus showing the ab3A is indeed “empty.” Lower traces were excitatory responses induced by DEET, IR3535, and picaridin and recorded from ab3 sensilla of Or42-expressing flies (w; Δhalo; UAS-DmOr42a/Or22a-GAL4).</p

Extracellularly recorded single unit responses from an ab3 sensillum.

<p>Spontaneous activity (upper trace) and picaridin-induced excitatory response (lower trace) from the large amplitude neuron, ab3A. Source dose, 100 µg. Note the excitatory responses lasted beyond the stimulus period.</p