Electrophysiological characterization of olfactory cell types in the antennae and palps of the housefly

A set of odours was presented to the housefly Musca domestica and the electrophysiological responses of single olfactory receptor cells in the antennae and palps were recorded. The olfactory cells in the antennae of the housefly showed a large variability of response profiles, but multidimensional cluster analysis suggested a moderate clustering in olfactory response types. Receptor cells with similar or with different odour response profiles can reside in one and the same sensillum. No fixed spatial distribution of olfactory response types over the antennal of palpal surface was found. The odours of 1-octen-3-ol, amyl acetate, 3-methylphenol, 2-pentanone and R(+)limonene elicited the largest responses in antennal cells. Most odours elicited responses in cells of only a few of the clusters, but 1-octen-3-ol was detected by cells of almost all clusters of the antenna. Surprisingly, rather low responses were found to acetic acid, skatole, indole and muscalure, odours that are known to attract flies. Response profiles of palpal cells differed considerably from those of antennal cells. Palpal cells mostly responded to 3-methylphenol and 2-pentanone. In the palps, the clusters of cells responding to 3-methylphenol and 2-pentanone are clearly separated from the other olfactory cells.