Nigrostriatal and mesolimbic Dreceptor expression in Parkinson's disease patients with compulsive reward-driven behaviors.
AUTHORS
- PMID: 29483278 [PubMed].
ABSTRACT
The nigrostriatal and mesocorticolimbic dopamine networks regulate reward-driven behavior. Regional alterations to mesolimbic dopamine Dreceptor expression are described in drug-seeking and addiction disorders. Parkinson’s disease (PD) patients are frequently prescribed D-like dopamine agonist (DAgonist) therapy for motor symptoms, yet a proportion develop clinically significant behavioral addictions characterized by impulsive and compulsive behaviors (ICBs). Until now, changes in Dreceptor binding in both striatal and extrastriatal regions have not been concurrently quantified in this population. We identified 35 human PD patients (both male and female) receiving DAgonist therapy, with (n=17) and without (n=18) ICBs, matched for age, disease duration, disease severity, and dose of dopamine therapy. In the off-dopamine state, all completed PET imaging with [F]fallypride, a high affinity D-like receptor ligand that can measure striatal and extrastriatal Dnondisplaceable binding potential (BP). Striatal differences between ICB+/ICB- patients localized to the ventral striatum and putamen, where ICB+ subjects had reduced BPIn this group, self-reported severity of ICB symptoms positively correlated with midbrain Dreceptor BPGroup differences in regional DBPrelationships were also notable: ICB+ (but not ICB-) patients expressed positive correlations between midbrain and caudate, putamen, globus pallidus, and amygdala BP’s. These findings support the hypothesis that compulsive behaviors in PD are associated with reduced ventral and dorsal striatal Dexpression, similar to changes in comparable behavioral disorders. The data also suggest that relatively preserved ventral midbrain dopaminergic projections throughout nigrostriatal and mesolimbic networks are characteristic of ICB+ patients, and may account for differential DAgonist therapeutic response.The biologic determinants of compulsive reward-based behaviors have broad clinical relevance, from addiction to neurodegenerative disorders. Here, we address biomolecular distinctions in Parkinson’s disease patients with impulsive compulsive behaviors (ICBs). This is the first study to image a large cohort of ICB+ patients using positron emission tomography with [18F]fallypride, allowing quantification of D2/3 receptors throughout the mesocorticolimbic network. We demonstrate widespread differences in dopaminergic networks, including (1) D2-like receptor distinctions in the ventral striatum and putamen, and (2) a preservation of widespread dopaminergic projections emerging from the midbrain, which is associated with the severity of compulsive behaviors. This clearly illustrates the roles of D2/3 receptors and medication effects in maladaptive behaviors, and localizes them specifically to nigrostriatal and extrastriatal regions.
The nigrostriatal and mesocorticolimbic dopamine networks regulate reward-driven behavior. Regional alterations to mesolimbic dopamine Dreceptor expression are described in drug-seeking and addiction disorders. Parkinson’s disease (PD) patients are frequently prescribed D-like dopamine agonist (DAgonist) therapy for motor symptoms, yet a proportion develop clinically significant behavioral addictions characterized by impulsive and compulsive behaviors (ICBs). Until now, changes in Dreceptor binding in both striatal and extrastriatal regions have not been concurrently quantified in this population. We identified 35 human PD patients (both male and female) receiving DAgonist therapy, with (n=17) and without (n=18) ICBs, matched for age, disease duration, disease severity, and dose of dopamine therapy. In the off-dopamine state, all completed PET imaging with [F]fallypride, a high affinity D-like receptor ligand that can measure striatal and extrastriatal Dnondisplaceable binding potential (BP). Striatal differences between ICB+/ICB- patients localized to the ventral striatum and putamen, where ICB+ subjects had reduced BPIn this group, self-reported severity of ICB symptoms positively correlated with midbrain Dreceptor BPGroup differences in regional DBPrelationships were also notable: ICB+ (but not ICB-) patients expressed positive correlations between midbrain and caudate, putamen, globus pallidus, and amygdala BP’s. These findings support the hypothesis that compulsive behaviors in PD are associated with reduced ventral and dorsal striatal Dexpression, similar to changes in comparable behavioral disorders. The data also suggest that relatively preserved ventral midbrain dopaminergic projections throughout nigrostriatal and mesolimbic networks are characteristic of ICB+ patients, and may account for differential DAgonist therapeutic response.The biologic determinants of compulsive reward-based behaviors have broad clinical relevance, from addiction to neurodegenerative disorders. Here, we address biomolecular distinctions in Parkinson’s disease patients with impulsive compulsive behaviors (ICBs). This is the first study to image a large cohort of ICB+ patients using positron emission tomography with [18F]fallypride, allowing quantification of D2/3 receptors throughout the mesocorticolimbic network. We demonstrate widespread differences in dopaminergic networks, including (1) D2-like receptor distinctions in the ventral striatum and putamen, and (2) a preservation of widespread dopaminergic projections emerging from the midbrain, which is associated with the severity of compulsive behaviors. This clearly illustrates the roles of D2/3 receptors and medication effects in maladaptive behaviors, and localizes them specifically to nigrostriatal and extrastriatal regions.