Fig. 7. Behavioral adaptation to either 100 µmol l^-1 PPNDS (pyridoxal-phosphate naphthylazo-nitro-disulfate) or 25 µmol l^-1 ß,-methylene ATP is associated with a reversible loss of external [³²P]ATP binding. (A) When assayed as a function of time, the % [³²P]ATP bound to live cells decreased over 15 min exposure to 100 µmol l^-1 PPNDS. (B) When the % [³²P]ATP bound to live cells was assayed after a 15 min exposure to either 25 µmol l^-1 ß,-methylene ATP or 100 µmol l^-1 PPNDS, both caused dramatic decreases in [³²P]ATP binding. When cells were adapted to either 25 µmol l^-1 ß,-methylene ATP or 100 µmol l^-1 PPNDS, washed free of the adapting ligand and then `de-adapted' in wash buffer for 15 min, the [³²P]ATP binding returned to normal levels. This showed that the adaptation was reversible. Each point represents the mean ± S.D. of three trials.