Gambling Rats

     In an experiment, Pramipexole (PPX), a dopamine agonist medication, was tested for possible effects in regards to pathological gambling and other impulse control disorders. For the experiment, the researchers found that PPX did, in fact, increase rats’ partiality for rewards associated with gambling. The reasoning for this was hypothesized that PPX has a “greater affinity for the D3 receptor subtype which was expressed predominantly in the limbic areas of the brain”.

     To conduct the study, the researchers produced three different experiments that resulted in various findings. Eight fourteen week old male Wistar rats were used in the experiment. None of the eight rats had been used in any previous experimentation. The eight rats underwent preliminary training and then moved onto a series of 21-trial blocks that lasted for four hours each. In the block trials, the first sixteen were forced-choice and then the last five were free-choice. These trails all took place within operant conditioning chambers.

     In setting up the experiment, the researchers had to establish what level of gambling was considered a low or high baseline. After that was decided, the researchers administered the saline test and then the PPX in a descending dose order. These doses were given subcutaneously ten minutes before each session. The effects of PPX, in relation to influencing gambling, was analyzed categorizing dose and series using the two-way repeated measures analysis variance.

     After conducting the study, researchers found that in the low gambling baseline, PPX made no difference between a free choice response and a forced-choice. In the high gambling baseline, at high doses of PPX, it significantly decreased the likelihood of perseveration. It was also found that agonist medication, such as PPX, can alter a human’s capabilities to learn from negative outcomes. PPX was also found to possibly leading to an increased chance of acting impulsively due to an individual only seeking immediate rewards; this can lead to an increase in gambling even though rewards may be occasional. 

Abstract 

Johnson, P. S., Madden, G. J., Stein, J. S. (2012). Effects of acute pramipexole on male rats’  preference for gambling-like rewards II. Experimental and Clinical Psychopharmacology, 20(3), 167-172. doi: 10.1037/a0027117