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Dopamine release and uptake dynamics within nonhuman primate striatum in vitro
S J Cragg1, C J Hille, S A Greenfield
1University Department of Pharmacology, Oxford, OX1 3QT, United Kingdom. stephanie.cragg@pharm.ox.ac.uk
Summary
Dopamine (DA) levels and regulation vary significantly across primate putamen regions, especially in areas vulnerable to Parkinson's disease (PD). These findings highlight crucial differences from rodents for understanding brain function and disease.
Area of Science:
- Neuroscience
- Neurochemistry
- Parkinson's Disease Research
Background:
- The putamen, a key part of the striatum, is the primary site of dopamine (DA) loss in Parkinson's disease (PD).
- Functional domains within the putamen exhibit heterogeneous susceptibility to DA loss.
- Dynamic regulation and regional comparisons of extracellular DA concentration ([DA](o)) in the primate brain remain underexplored.
Purpose of the Study:
- To investigate the real-time dynamics of extracellular dopamine ([DA](o)) in different functional domains of the primate putamen.
- To compare dopamine regulation and availability between primate and rodent striata.
- To understand the implications of regional DA heterogeneity for Parkinson's disease and drug responses.
Main Methods:
- Fast-scan cyclic voltammetry was used to measure DA in vitro in striatal sections of the common marmoset (Callithrix jacchus).
- DA uptake mechanisms were characterized using specific transporter inhibitors.
- Data modeling with Michaelis-Menten kinetics simulations was employed to determine kinetic parameters like V(max).
Main Results:
- Extracellular DA ([DA](o)) released by a single stimulus varied threefold along the ventromedial-dorsolateral axis.
- DA uptake primarily occurred via the DA transporter (GBR12909 sensitive, desipramine insensitive).
- Vmax, representing DA uptake capacity, and [DA](o) were highest in regions most vulnerable to PD, with significant interspecies differences compared to rodents.
Conclusions:
- Primate striatal DA dynamics exhibit significant interspecies heterogeneity compared to rodents.
- Regional variations in DA availability and regulation within the primate putamen are substantial.
- These findings are critical for extrapolating rodent-based findings to primates and for understanding DA's role in health, addiction, and diseases like PD.