Temporal pattern of lever pressing within test session. Minute-by-minute time-course of lever pressing peaks on sucrose-associated lever after microinjections of (A) vehicle, (B) amphetamine 20 μg, (C) CRF 500 ng, and (D) CRF 250 ng. Open circles depict lever pressing during presentation of the 30-sec CS- and filled circles during presentation of the CS+. Lever pressing is also shown during the 30 sec period before each CS+ or CS- (precue baseline), and during the 30 sec period that followed each CS+ or CS- (post-cue period). Both CRF (500 ng) and amphetamine (20 μg) magnified intense, transient, reversible, and repeatable peaks in pressing on sucrose-associated lever each time the CS+ occurred. Magnified lever pressing after CRF (500 ng) or amphetamine (20 μg) was triggered by each presentation of the sucrose cue, but then was followed by a rapid descent back to normal baseline levels of pressing once the cue ended (B and C).