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Choline acetyltransferase and somatostatin levels in aged Microcebus murinus brain
P Dournaud1, J P Gautron, E Pattou
1INSERM U159, Centre Paul Broca, Paris, France.
Abstract:
beta-Amyloid protein (beta-AP) deposits, analoguous to those found in Alzheimer's disease (AD) are observed in the brain of aging Microcebus murinus. Because choline acetyltransferase (ChAT) activity and somatostatin (SRIH) content are consistently decreased in AD, we tested whether such changes could be observed in middle aged to aged Microcebus cerebral cortex and whether they were accompanied by beta-AP deposits. A positive correlation was observed between age and ChAT activity. By HPLC, SRIH immunoreactivity eluted as four peaks, two of which being identical with SRIH-28 and SRIH-14 while the other two likely represented precursor forms. Cortical SRIH content was not significantly affected by age. ChAT activity and SRIH content were not significantly correlated. Amyloid angiopathy was observed in every brain examined and the presence of cortical lesions analoguous to senile plaques observed in the oldest case only which did not demonstrate important alterations in ChAT and somatostatin levels.
Insights
Aging Microcebus murinus brains show beta-amyloid deposits. Choline acetyltransferase activity increased with age, but somatostatin levels remained unchanged, unlike in Alzheimer's disease.
Area of Science:
- Neuroscience
- Aging Research
- Comparative Pathology
Background:
- Alzheimer's disease (AD) is characterized by beta-amyloid (beta-AP) deposits, decreased choline acetyltransferase (ChAT) activity, and reduced somatostatin (SRIH) levels.
- Aging Microcebus murinus primates exhibit beta-AP deposits in the brain, similar to AD pathology.
Purpose of the Study:
- To investigate age-related changes in ChAT activity and SRIH content in the cerebral cortex of Microcebus murinus.
- To determine if these neurochemical changes correlate with the presence of beta-AP deposits.
Main Methods:
- Analysis of ChAT activity and SRIH content in the cerebral cortex of middle-aged to aged Microcebus murinus.
- High-performance liquid chromatography (HPLC) to characterize SRIH immunoreactivity.
- Histopathological examination for beta-amyloid deposits and cortical lesions.
Main Results:
- A positive correlation was found between age and ChAT activity.
- Cortical SRIH content was not significantly affected by age, with four immunoreactive peaks identified, including SRIH-28 and SRIH-14.
- Amyloid angiopathy was prevalent in all examined brains; however, significant alterations in ChAT activity and SRIH levels were not observed even in the oldest cases with plaque-like lesions.
Conclusions:
- Aging Microcebus murinus display beta-AP deposition but lack the characteristic decrease in ChAT activity and SRIH content seen in Alzheimer's disease.
- These findings suggest that beta-AP deposition in aging primates may not directly parallel the neurochemical deficits associated with human Alzheimer's disease.