Limonoids such as deoxylimonin, obacunone and pedoniti are known to have antifeedant effects against some lepidopteran pests. However, there is no electrophysiological data showing the effect these compounds have on taste receptor cells. This information gap is due to the fact that limonoids are insoluble in water and this makes it difficult to apply the tip-recording technique in an electrophysiological bioassay of limonoids. This problem was solved by dissolving the limonoids in a mixture of 50 % tetrahydrof uran and 50 % aqueous NaCl. Limonoids and sucrose so dissolved were used to investigate responses of Eldana saccharina maxillary styloconic sensilla. The solvent mixture did not appear to damage the taste receptor cells and the taste receptor responses to solutes dissolved in that solvent were reproducible. Sucrose stimulated a cell in the medial as well as in the lateral styloconic sensilla. Deoxylimonin alone stimulated a cell in the medial sensillum but not in the lateral sensillum. When presented with sucrose, deoxylimonin inhibited the sugar receptor cell and this was also true for obacunone.
