THE EFFECTS OF G-PROTEIN MODULATORS ON THE LABELLAR TASTE RECEPTOR-CELLS OF THE FLESHFLY (BOETTCHERISCA-PEREGRINA)

A nonhydrolyzable G protein activator (guanosine 5'-O-(3-thiotriphosph ate); GTP gamma S) and a G protein inhibitor (guanosine 5'-O-(2-thiodi phosphate); GDP beta S) were introduced into the labellar taste recept or cells of the fleshfly by treatment of their receptive membranes ben eath the tip opening of the chemosensory hair with each reagent in 0.0 3% deoxycholate solution for 4 min, After treatment with GTP gamma S, the responses of the sugar receptor cell to D-glucose, D-fructose, L-p henylalanine and L-valine and that of the salt receptor cell to cyclic AMP were markedly enhanced, compared with those after treatment with deoxycholate alone, Treatment with GDP beta S depressed these response s, These results strongly suggest that the responses are mediated by G protein. However, the response of the salt receptor cell to NaCl was not affected by treatment with either GTP gamma S or GDP beta S, and t hus the response to NaCl clearly is not elicited through a G protein-r egulated mechanism. (C) 1997 Elsevier Science Ltd.