Fig. 2.

Functional analysis of the olfactory receptor (OR)-evoked responses in vivo and in vitro. (A,B) Single sensillum recording (SSR) technique. (A) Drawing of a Drosophila head. During SSR, the recording electrode is positioned in the sensilla located on the 3rd segment of the antenna. (B) Responses of Drosophila melanogaster antennal basiconic sensilla to methyl acetate using SSR. The A cell (blue spikes) responds to increasing concentrations of the odorant, while the B cell (green spikes) is unaffected. (C,D) Ca²⁺-imaging technique. (C) Schematic of Ca²⁺-imaging assay of human embryonic kidney 293 (HEK293) cells. The cells, #1 and #2, are loaded with a Ca²⁺-sensitive dye and the light emission of the dye is monitored through a microscope while the cells are stimulated with odorants. The cells marked with broken circles show an increase of Ca²⁺ concentration after odorant stimulation. (D) A representative trace showing the dose-dependent response to indole of cell #2 (panel C) expressing the mosquito Anopheles gambiae receptors GPROR10+GPROR7. Arrowheads indicate the increasing concentration of odorant delivered (μmol l^–1).