Effects of bath-applied slowly reversible antagonists BTMPS (A), TMPH (B), and tkP3BzPB (C and D) on responses of α7 nAChRs expressed in oocytes to 60 or 10 µM ACh plus 10 μM PNU-120596 (PNU). After measuring two baseline responses evoked by ACh alone or ACh plus PNU-120596, the antagonist solution was added to the bath for 15 minutes, followed by a 10- to 15-minute washout. The oocytes were repeatedly probed for their ACh or ACh plus PNU-120596 responses. All points represent averaged normalized data (± S.E.M., n ≥ 4) of peak current responses for each condition. Note that since low concentrations of TMPH were ineffective and inhibited a run up of potentiated responses, the scale of (B) is expanded relative to the other plots.