Examining the effects of d-amphetamine on discounting in spontaneously hypertensive rats (SHR)

This experiment examined d-amphetamine’s effect on discounting of delayed and probabilistic outcomes in spontaneously hypertensive rats (SHRs), a purported animal model of Attention Deficit/Hyperactivity Disorder (ADHD), with two control strains. Stimulants such as d-amphetamine are commonly administered in humans diagnosed with ADHD, thus resulting in increases in self-controlled responding on delay tasks. However, very little has been done examining the effects of d-amphetamine on delay tasks using the SHR strain, a purported animal model of ADHD. Recent research has also suggested that responses on delay and probability discounting procedures are mediated by the same underlying mechanism in animal models (Green, Myerson & Calvert, 2010). However, this equivalence is not observed when using human participants in similar choice procedures. The current experiment used an adjusting amount procedure to measure the subjective value of delayed and probabilistic reinforcers and the effects of d-amphetamine on choice behavior. The standard reinforcer varied across 8 conditions (5 pellets, each evaluated at two delays: 2 and 16-s and across two probabilities: VR-2 and VR-10. Each condition was run with both d-amphetamine [1.0mg/kg] and a saline vehicle.). The current results suggest non-equivalence as d-amphetamine appears to have differential effects on the choice behavior across different strains of rats. The current findings suggest that d-amphetamine appears to have differential effects on subjective values in the delay and probability discounting tasks