Effects of pramipexole on impulsive choice in male wistar rats

Abstract

Clinical reports, primarily with Parkinson's disease patients, note an association between the prescribed use of pramipexole (and other direct-acting dopamine agonist medications) and impulse control disorders, particularly pathological gambling. Two experiments examined the effects of acute pramipexole on rats' impulsive choices where impulsivity was defined as selecting a smaller-sooner over a larger-later food reward. In Experiment 1, pramipexole (0.1 to 0.3 mg/kg) significantly increased impulsive choices in a condition in which few impulsive choices were made during a stable baseline. In a control condition, in which impulsive choices predominated during baseline, pramipexole did not significantly change the same rats' choices. Experiment 2 explored a wider range of doses (0.01 to 0.3 mg/kg) using a choice procedure in which delays to the larger-later reinforcer delivery increased across trial blocks within each session. At the doses used in Experiment 1, pramipexole shifted choice toward indifference regardless of the operative delay. At lower doses of pramipexole (0.01 and 0.03 mg/kg), a trend toward more impulsive choice was observed at the 0.03 mg/kg dose. The difference in outcomes across experiments may be due to the more complex discriminations required in Experiment 2, that is, multiple discriminations between changing delays within each session.

Figure 1

Average (SEM) percent of trials omitted per session (top panel) and mean center lever response latency (bottom panel) as a function of saline and pramipexole doses in Experiment 1.

Figure 2

Average (SEM) percent choice of the impulsive (SS) alternative in impulsive and self-control baseline conditions of Experiment 1.

Figure 3

Average (SEM) percent choice of the impulsive (SS) alternative in impulsive and self-control baseline conditions of Experiment 1. Data were excluded from analysis if the rats completed fewer than 50% of free-choice trials in a session.

Figure 4

Average (SEM) percent choice of the LL reward as a function of LL delay across trial blocks in Experiment 2. The top panel displays choices made at the same doses used in Experiment 1. The bottom panel shows choices made at two smaller doses.