Fig. 3. Inhibition of PDF-degrading activity of D. melanogaster head membranes by phosphoramidon and thiorphan. Inhibition curves for phosphoramidon (filled triangles, IC₅₀=0.15 µmol l^–1) and thiorphan (open squares, IC₅₀=1.2 µmol l^–1) were generated by measuring the formation of PDF8-18 from PDF in the presence of different concentrations of inhibitors, as described in Materials and methods. Data are expressed relative to uninhibited activity and IC₅₀ values were calculated using FigP (Biosoft).