Fig. 6. Behavioral cross-adaptation seen as a function of time in either 25 µmol l^-1 ß,-methylene ATP (met-ATP) or 100 µmol l^-1 PPNDS (pyridoxal-phosphate naphthylazo-nitro-disulfate). Cross-adaptation between two ligands is seen as the loss of responsiveness to one ligand following exposure to the other ligand and vice versa. (A) Cells were adapted to 25 µmol l^-1 ß,-methylene ATP and then retested in either 25 µmol l^-1 ß,-methylene ATP (open circles) or 100 µmol l^-1 PPNDS (filled circles). Cross-adaptation was seen in response to either ligand with similar time courses. (B) Cross-adaptation was also demonstrated by incubation in 100 µmol l^-1 PPNDS and retesting in either 25 µmol l^-1 ß,-methylene ATP (open circles) or 100 µmol l^-1 PPNDS (filled circles). Each point represents the mean ± S.D. of three trials.