Fig. 3.

Effects of different doses of diphenhydramine (DPH; 0.3–1.7 mg/kg per injection) in combination with cocaine (0.03 mg/kg per injection) on operant responding under a second-order schedule of reinforcement in rhesus monkeys (n=3). a, b, and c show individual mean data for the last three behavioral sessions during which the variance was less than 20%. d is shown as mean±SEM normalized as percent control of cocaine-maintained operant responding for each component of the behavioral sessions. Asterisk indicates significantly different from saline and cocaine alone within that component. # indicates significantly different from cocaine only, + indicates significantly different from saline only