The expression of Gr59c^Scer\UAS.cDa under the control of Scer\GAL4^Gr89a.2 leads to the following electrophysiological response changes of labellar sensilla to bitter tastants, as compared to controls: I-a, I-b and S-a sensilla display significantly increased responses to (-)-lobeline HCl, Denatonium benzoate (which is also a novel response in I-b sensilla) and Berberine chloride; I-b sensilla also display significantly decreased responses to Theobromine, Caffeine, Umbelliferone and Theophylline; S-a sensilla also display significantly decreased responses to Umbelliferone, D-(+)-sucrose octaacetate, Azadirachtin, Aristolochic acid and Strychnine nitrate salt; these labellar sensilla types display no significant electrophysiological response changes to Rotenone, N,N-Diethyl-m-toluamide, Escin, Gossypol, Cucurbitacin I hydrate, Myricetin, Coumarin, Saponin, Sparteine sulfate salt and Quinine.