Figure 3.

Bitter-sensitive cells respond also to inhibitory sexual pheromones. (A) Diagram showing the two electrodes configuration used to record extracellular activities from taste sensilla of Drosophila. In all cases, a glass capillary containing the stimulus is used to cap the tip of a gustatory sensillum. If the stimulus is water-soluble, the stimulus electrode can contain an electrolyte and can be used to record electrical signals from the neurons within the sensilla. If the stimulus is lipophilic, the stimulus electrode which contains paraffin oil with the ligand, is no longer conductive and we use another electrode, for example a fine tapered tungsten rod, inserted at the base of a sensillum. (B) Sample recordings obtained from an I-type sensillum on the proboscis of Drosophila using a tungsten recording electrode, and stimulating either with sucrose (suc), caffeine (caff), 7-tricosene (7-T) or a mixture of 7-tricosene and caffeine (reproduced from Lacaille et al., 2007).