Impact of Monoamine Transport Inhibitors in the Rat Gambling Task

Dysfunctional decision-making is characteristic of numerous psychiatric disorders including schizophrenia, mood disorders, ADHD, eating disorders, pathological gambling and substance abuse. The rodent Gambling Task (rGT) is analogous to the Iowa Gambling Task (IGT) and models risky decision-making in rodents. The rGT has unique response options that range from high probability of small rewards and lower probability of penalty to responses that result in low probability of larger reward and higher probability of penalty. Similar to the IGT, the optimal rGT strategy is exclusive choice of an intermediate reward/penalty response option. Importantly, similar baseline behavior exists between human and rodent subjects and supports the validity of the rGT in examining different behavioral phenotypes. In addition to strong face and construct validity, the rGT measures motor impulsivity and decision-making behaviors and integration- or dissociation- of these two behaviors is essential to characterizing the impact of different neurobiological or pharmacological manipulations. Due to monoamines' (dopamine, serotonin and norepinephrine) integral role in the modulation of reward assessment and impulsivity, we examined the impact of several monoaminergic-altering drugs: d-amphetamine, eticlopride, cocaine, methylphenidate (Ritalin), and bupropion (Wellbutrin). Although each drug differed in mechanism of action and affinity for specific monoamine transporters, only slight behavioral differences were observed in the rGT. Interestingly, all monoamine-enhancing drugs increased selection of the lowest risk option and significantly shifted behavior away from the optimal response.