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Muscarinic receptor concentrations and dopamine release in aged rat striata
K Yamagami1, J A Joseph, G S Roth
1Molecular Physiology and Genetics Section, NIA Francis Scott Key Medical Center, Baltimore, MD 21224.
Abstract:
The extent to which age-related decreases in muscarinic enhancement of K(+)-evoked dopamine release (K(+)-ERDA) from perifused striatal slices is dependent upon the loss of striatal muscarinic receptors (mAChR) was determined. Both K(+)-ERDA and mAChR (M1, M2) concentrations were assessed from the same animals (3, 5-7 and 24-27 months). Results indicated associated decreases of 70% in oxotremorine-enhanced K(+)-ERDA and 36% in Bmax (3H-QNB) (3 and 24-27 months groups). Decrease of mAChR Bmax was not the result of membrane sequestration. Although both the concentrations of M1 and M2 muscarinic receptor subtypes decline with age, only the M2 receptor decline was correlated with the age-related decreases in muscarinic enhancement of K(+)-ERDA (r = .71, p less than 0.001). Results suggest that age-related decreases in mAChR concentrations as being partially responsible for deficits in muscarinic enhancement of K(+)-evoked release of DA.
Insights
Age-related dopamine release deficits are linked to fewer muscarinic receptors. Specifically, the decline in M2 muscarinic receptors correlates with reduced dopamine release in aging brains.
Area of Science:
- Neuroscience
- Aging Research
- Pharmacology
Background:
- Age-related cognitive decline is associated with altered neurotransmitter systems.
- Muscarinic acetylcholine receptors (mAChR) play a crucial role in regulating dopamine release.
- Understanding the impact of aging on mAChR function is vital for addressing neurodegenerative conditions.
Purpose of the Study:
- To determine the extent to which age-related decreases in muscarinic enhancement of potassium-evoked dopamine release (K(+)-ERDA) depend on the loss of striatal mAChR.
- To investigate the correlation between specific mAChR subtypes (M1 and M2) and age-related changes in dopamine release.
Main Methods:
- Assessed K(+)-ERDA and mAChR concentrations (M1, M2) in striatal slices from young (3 months) and aged (24-27 months) animals.
- Utilized oxotremorine to enhance K(+)-ERDA and quantified mAChR binding using (3H-QNB).
- Analyzed the correlation between receptor subtype concentrations and dopamine release parameters.
Main Results:
- A 70% decrease in oxotremorine-enhanced K(+)-ERDA was observed in aged animals compared to young animals.
- A significant decrease (36%) in mAChR maximal binding capacity (Bmax) was found in aged rats.
- The decline in M2 mAChR concentration, but not M1, was significantly correlated with the age-related reduction in muscarinic enhancement of K(+)-ERDA (r = .71, p < 0.001).
Conclusions:
- Age-related decreases in striatal mAChR concentrations partially contribute to deficits in muscarinic enhancement of K(+)-evoked dopamine release.
- The M2 muscarinic receptor subtype appears to be a key player in the age-associated decline of dopamine regulation.
- These findings highlight the importance of mAChR function in maintaining dopaminergic neurotransmission during aging.