Objective: To identify common clinical and imaging abnormalities in Parkinson’s disease patients and heroin-dependent patients compared with healthy controls in order to better understand the pathophysiology underlying neuropsychiatric symptoms in Parkinson’s disease and substance addiction.

Background: Parkinson’s disease patients on dopaminergic replacement therapy are at increased risk of developing behavioral addictions, with a prevalence of impulsive control disorder behaviors reaching up to 35%, compared with the 20% in the general population. Thus, someone could ask: how dopaminergic replacement therapy contributes to the occurrence of addictions in Parkinson’s disease patients?

Method: We compared twenty Parkinson’s disease patients with motor and neuropsychiatric fluctuations with twenty sex-matched heroin-dependent patients and twenty-seven healthy controls. Participants underwent a functional MRI (fMRI) at rest in a crossover design under two treatment conditions (drug-on and drug-off). Healthy controls were studied in only one condition. From the fMRI time-courses, we extracted co-activation patterns (CAP) of limbic, executive and motor striatum and we analyzed their temporal and spatial characteristics.

Results: Compared with healthy controls, Parkinson’s disease and heroin-dependent patients presented with common behavioral features with: i) a higher “lack of perseverance” on the impulsivity scale, ii) a higher degree of behavioral and substance addiction and iii) a higher score of depression. We found that during the drug-on state, both heroin-dependent and Parkinson’s disease participants presented, as compared to the drug-off state and to HC, an increased occurrence of CAPs between the striatum and the orbito- and pre-frontal cortex and a reduced occurrence of CAPs between the supplementary motor area and the pre-frontal cortex. These changes in CAPs occurrence correlated with the severity of the addictive (hyperdopaminergic) behavioral disorders.

Conclusion: These preliminary results demonstrate similar clinical and functional connectivity alterations in heroin-dependent and Parkinson’s disease patients, hinting to treated Parkinson’s disease as a neurodegenerative model to study addiction.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/is-dopamine-replacement-therapy-an-addictive-drug/