The expression of Gr2a^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 sensilla display novel responses to Caffeine, Umbelliferone and Theophylline, and a significantly increased response to (-)-lobeline HCl; S-a sensilla display significantly decreased responses to Denatonium benzoate, Sparteine sulfate salt, Strychnine nitrate salt, Azadirachtin and (-)-lobeline HCl; I-b sensilla display no significant changes to the aforementioned tastants; these labellar sensilla types display no significant electrophysiological response changes to Rotenone, N,N-Diethyl-m-toluamide, Escin, Gossypol, Theobromine, Cucurbitacin I hydrate, D-(+)-sucrose octaacetate, Aristolochic acid, Myricetin, Coumarin, Saponin, Quinine, and Berberine chloride.