Figure 1. Functional characterization of the AgOrs.

(a) Extracellular recordings from the empty neuron expressing an AgOr. Top, excitatory response of AgOr2 to 2-methylphenol; middle, excitatory response of AgOr21 to 6-methyl-5-hepten-2-one; bottom, inhibitory response of AgOr1 to 6-methyl-5-hepten-2-one. Action potentials from both neurons housed in the sensillum can be observed and distinguished by amplitude; the larger-amplitude action potential, from the ‘A’ neuron, expresses the AgOr, while the smaller-amplitude action potential, from the ‘B’ neuron, expresses its endogenous D. melanogaster odourant receptor⁹. (b) Left, odourant response profile of AgOr8 expressed in the empty neuron. Right, odourant response profile of the An. gambiae neuron that houses AgOr8 (adapted from Lu, et al., 2007). All odourants were tested at a dilution of 10⁻². The spontaneous firing rate and the responses to the diluent are subtracted from odourant responses in each panel. Of the 28 odourants that inhibited the spontaneous firing rate by 50% or more in the empty neuron⁴⁷, 21 gave mean responses that were negative in the endogenous An. gambiae neuron. Error bars represent SEM. (c) Heat map of responses of the 50 functional AgOrs to 110 odourants. Response intensity is colour-coded according to the continuous colour scale on the right and represents the mean activity measured over a 0.5 second odourant stimulation period. Receptors, odourants, and numerical values are indicated in Supplementary Table 2. n = 5–6; for odourants that elicit responses ≥100 spikes/second, n = 6. Spontaneous activity and responses to diluent have been subtracted from response values. All odourants were tested at a 10⁻² dilution. Odourants containing both a phenol ring and an ester moiety are classified as aromatics; terpenes containing an ester moiety are classified as terpenes.