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Dopamine release and uptake rates both decrease in the partially denervated striatum in proportion to the loss of
P A Garris1, Q D Walker, R M Wightman
1Department of Biological Sciences, Illinois State University, Normal 61790-4120, USA.
Brain Research
|April 11, 1997
Summary
Normal extracellular dopamine levels are maintained in partially denervated striata without active compensation. Passive mechanisms, not neuronal adjustments, preserve dopamine function in early Parkinson's disease.
Area of Science:
- Neuroscience
- Neuropharmacology
Background:
- The striatum plays a crucial role in motor control, and its dopamine system is implicated in Parkinson's disease.
- Parkinson's disease is characterized by the progressive loss of dopamine-producing neurons, leading to motor deficits.
Purpose of the Study:
- To investigate whether extracellular dopamine concentrations are preserved in a partially denervated striatum.
- To determine if active compensatory changes in dopamine uptake or release occur in response to partial denervation.
Main Methods:
- Adult rats underwent unilateral 6-hydroxydopamine lesions to partially denervate the striatum.
- Fast-scan cyclic voltammetry with carbon-fiber microelectrodes was used to monitor extracellular dopamine levels in vivo.
- Tissue dopamine content was measured using High-Performance Liquid Chromatography with Electrochemical Detection (HPLC-EC).
Main Results:
- Extracellular dopamine concentrations elicited by stimulation were similar in lesioned and control striata, despite a 30-70% decrease in tissue dopamine.
- Vmax for dopamine uptake and dopamine release per stimulus pulse decreased proportionally to the lesion size.
- These findings indicate preserved extracellular dopamine without active neuronal compensation.
Conclusions:
- Normal extracellular dopamine levels can be maintained in a partially denervated striatum through passive regulatory mechanisms.
- These passive mechanisms are crucial for maintaining striatal function during the preclinical or presymptomatic stages of Parkinson's disease.