Effects of prenatal stress on lever-press acquisition with delayed reinforcement in male and female rats

► Acquisition with delayed reinforcement was examined in male and female prenatally stressed (PS) and control (CON) rats. ► Twice as many PS male rats than PS female, CON male, and CON female rats acquired the response. ► PS males responded at significantly higher rates on the operative lever and earned significantly more reinforcers than the other groups. ► PS rats showed enhanced learning with a positive-reinforcement task, and this effect of PS was specific for male rats. The prenatally stressed (PS) rat shows enhanced conditioned fear and increased behavioral inhibition in response to footshock compared to control (CON) rats. It is unclear whether this facilitated learning will occur only with aversive stimulation, or if it will also be observed in the context of positive reinforcement. There are limited and inconsistent data regarding sex differences and the impact of prenatal stress on learning. The present study was designed to examine lever-press acquisition with a 10-s delay to food reinforcement in male and female PS and CON rats. Overall, twice as many PS male rats acquired the lever-press response than the PS female rats, CON male rats, and CON female rats. PS male rats also earned significantly more reinforcers and responded on the operative lever at a significantly greater rate than the other three rat groups. These findings suggest that PS rats exhibit altered learning with a task involving positive reinforcement, and this effect of PS is sex specific for male rats.