| Abstract No.: | 317 |
| Country: | Canada |
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| Title: | Does Too Much or Too Little Dopamine Confer Vulnerability to Drug Addiction? |
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| Authors/Affiliations: | Alain Dagher, MD
McGill University, Montreal, QC, Canada |
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| Content: | There is considerable evidence linking dopamine to addiction, however questions remain regarding the mechanisms involved. Dopamine is clearly involved in reinforcement and learning, and it appears that inherited and acquired differences in dopaminergic function convey vulnerability to addiction. For example, there are considerable differences in baseline D2 receptor density in the striatum of healthy humans, and these are correlated to personality dimensions such as novelty seeking and impulsivity, which are associated with addiction, and to differences in the ability to learn about rewards and punishments.
Animal and human experiments suggest that hyper-responsivity of the dopamine system to drugs or stressors may be associated with vulnerability to addiction. In addition, patients who suffer from Parkinson’s disease may illuminate the issue. These patients typically display a rigid, neo-phobic personality, and have a very low incidence of addiction. However, when certain patients are treated with dopaminergic medications, especially dopamine receptor agonists, they develop impulsivity as well as severe behavioral addictions such as pathological gambling. These problems typically resolve upon discontinuation or reduction of the medication. This suggests that tonic dopaminergic stimulation, possibly acting in the ventral striatum, is associated with impulsivity and addiction.
However, an entirely separate school of thought argues that it is dopamine deficiency that promotes addiction. This theory, referred to as the “reward deficiency syndrome” model, proposes that chronically low dopamine levels cause individuals to seek stimulating experiences and substances as a form of self-medication. There is also much evidence to support this view.
Finally it is possible that both high and low tonic dopamine levels act as potential pathways to addiction and impulsivity. This presentation will review the animal and human evidence supporting both models.
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