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Differential declines in striatal nicotinic receptor subtype function after nigrostriatal damage in mice
Maryka Quik1, Jocelyn D Sum, Paul Whiteaker
1The Parkinson's Institute, Sunnyvale, California 94089-1605, USA. mquik@parkinsonsinstitute.org
Molecular Pharmacology
|April 16, 2003
Summary
Nigrostriatal damage from MPTP reduces striatal nicotinic acetylcholine receptors (nAChRs) and their function, particularly alpha-conotoxin MII-sensitive subtypes. These changes correlate with dopamine transporter loss, suggesting functional significance in Parkinson's disease.
Area of Science:
- Neuroscience
- Pharmacology
- Neurodegenerative Diseases
Background:
- Nigrostriatal pathway damage is linked to reduced striatal nicotinic acetylcholine receptors (nAChRs) in Parkinson's disease and animal models.
- Previous studies indicate a reduction in nAChR binding sites, but their functional implications and specific subtype involvement remain unclear.
Purpose of the Study:
- To investigate if nigrostriatal damage alters striatal nAChR function.
- To identify specific nAChR subtypes affected by nigrostriatal damage.
- To correlate changes in nAChR binding and function with dopaminergic terminal integrity.
Main Methods:
- Induced nigrostriatal damage in mice using the dopaminergic toxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP).
- Measured binding of radioligands for dopamine transporter and various nAChR subtypes (alpha-conotoxin MII-sensitive/resistant, beta2, alpha 7).
- Assessed nAChR function using neurotransmitter release ([3H]dopamine, [3H]GABA) and ion flux ([86Rb+] efflux) assays.
Main Results:
- MPTP treatment significantly reduced striatal dopamine transporter levels.
- Both binding and functional measures of alpha-conotoxin MII-sensitive nAChRs decreased post-MPTP.
- Selected measures of alpha-conotoxin MII-resistant nAChRs also showed declines, while alpha-7 nAChR binding remained unchanged.
- Changes in striatal nAChRs correlated with dopamine transporter declines, indicating localization to dopaminergic terminals.
- No significant nAChR declines were observed in other brain regions like the cortex, thalamus, or septum.
Conclusions:
- Demonstrates differential alterations in nAChR subtype function following nigrostriatal damage.
- Highlights a strong correlation between reduced nAChR binding and function, particularly for alpha-conotoxin MII-sensitive subtypes.
- Suggests that observed nAChR declines in Parkinson's disease may have significant functional consequences.