Impacts of reward schedules and a dopamine agonist on dopamine receptor expression in an animal model of gambling addiction

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Laskowski, Catherine
University of Lethbridge. Faculty of Arts and Science
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Lethbridge, Alta. :University of Lethbridge, Dept. of Neuroscience
The unpredictable payouts of random-ratio schedules, like those used by slot-machines, are highly motivating. This is likely due to the relationship between unexpected rewards and dopamine neurons, which release dopamine in response to unexpected reward. Dopaminergic activity can also be increased by dopaminergic drugs which are used to treat Parkinson’s disease. These medications have been linked to gambling addiction. In a series of experiments, rats were assessed for addiction-like behaviours after working for food reward on either a random or fixed ratio schedule of reinforcement with the addition of a dopamine agonist, pramipexole in follow-up experiments. Rats that were trained on the random ratio schedule were highly motivated but did not exhibit other signs of addiction. When pramipexole was added, rats displayed additional addiction-like symptoms and their brains exhibited significant changes in dopamine receptor expression. In sum, both unpredictable reward schedules and dopamine agonists contribute to behaviours characteristic of addiction.
Neuroscience , Addiction medicine , Cognitive science , Gambling addiction , Reward schedules