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Relation between brain dopamine loss and D2 dopamine receptor density in MPTP monkeys
P Falardeau1, P J Bédard, T Di Paolo
1School of Pharmacy, Laval University, Québec, Canada.
Neuroscience Letters
|March 31, 1988
Summary
MPTP lesions in monkeys cause dopamine (DA) depletion, leading to increased D2 DA receptor binding. This suggests DA receptor supersensitivity develops when nerve fibers cannot compensate for DA loss.
Area of Science:
- Neuroscience
- Pharmacology
- Neurochemistry
Background:
- Dopamine (DA) plays a crucial role in motor control and reward pathways.
- Dopaminergic neurotoxicity, induced by MPTP, is a model for Parkinson's disease.
- D2 DA receptors are key targets in understanding DAergic system function.
Purpose of the Study:
- To investigate the relationship between dopamine metabolite levels and D2 DA receptor binding after MPTP-induced DAergic lesions in monkeys.
- To determine if DA receptor supersensitivity occurs following significant DA depletion.
Main Methods:
- MPTP was used to create DAergic lesions in monkeys.
- Concentrations of dopamine (DA), DOPAC, and HVA were measured.
- [3H]spiperone binding assays were performed to quantify D2 DA receptor density in specific brain regions (caudate nucleus, putamen, nucleus accumbens).
Main Results:
- DA depletion ranged from 37% to 100%.
- A significant elevation in [3H]spiperone binding density (114.8% of control) was observed with at least 90% DA depletion (P < 0.01).
- A logarithmic correlation was found between DA concentrations and D2 DA receptor binding density (r = -0.54, P < 0.01).
Conclusions:
- MPTP lesions in monkeys lead to significant D2 DA receptor upregulation.
- DA receptor supersensitivity develops when remaining dopaminergic nerve fibers are insufficient to compensate for DA loss.
- These findings provide insights into the neuroadaptive mechanisms following dopaminergic neurotoxicity.