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Cellular expression of somatostatin in MAM-induced microencephaly in the rat
Abstract:
Methylazoxymethanol acetate (MAM) is a mitotic inhibitor that has been used to selectively destroy neuroblasts at specific times during gestation. The administration of MAM results in a dose-dependent microencephaly. Following MAM treatment at 15 days of gestation, we have noted an increase in the level of SS immunoreactivity in the neocortex, as determined by radioimmunoassay. Northern blot analysis for preproSS mRNA revealed an increase in MAM-treated cortex. The cellular distribution of SS has been determined using in situ hybridization and immunocytochemistry. There was a 30% increase in the density of SS-immunoreactive neurons in the cortex of the MAM-treated animals. These data suggest that SS neurons in the cortex are spared following MAM treatment at GD 15.
Insights
Methylazoxymethanol acetate (MAM) causes microencephaly by destroying neuroblasts. However, SS neurons in the neocortex are spared and show increased immunoreactivity after MAM treatment during gestation.
Area of Science:
- Neuroscience
- Developmental Biology
- Toxicology
Background:
- Methylazoxymethanol acetate (MAM) is a known teratogen that induces microencephaly through selective neuroblast destruction.
- Understanding the differential vulnerability of neuronal populations to developmental insults is crucial for comprehending brain development and disorders.
Purpose of the Study:
- To investigate the effect of MAM administration on the developing neocortex, specifically focusing on somatostatin (SS) expressing neurons.
- To determine if SS neurons are selectively spared or affected by MAM-induced neurotoxicity during a critical period of gestation.
Main Methods:
- Administration of MAM to pregnant rodents at 15 days of gestation.
- Radioimmunoassay to quantify SS immunoreactivity levels in the neocortex.
- Northern blot analysis to assess preproSS mRNA expression.
- In situ hybridization and immunocytochemistry to determine the cellular distribution and density of SS-immunoreactive neurons.
Main Results:
- MAM treatment resulted in a dose-dependent microencephaly.
- A significant increase in SS immunoreactivity and preproSS mRNA levels was observed in the neocortex of MAM-treated animals.
- A 30% increase in the density of SS-immunoreactive neurons was found in the cortex of MAM-exposed brains.
- Cellular distribution analysis confirmed the increased presence of SS neurons.
Conclusions:
- SS neurons in the neocortex appear to be resistant to the neurotoxic effects of MAM when administered at 15 days of gestation.
- These findings suggest a potential protective mechanism or inherent resilience of SS neurons during specific developmental windows.
- The study highlights the differential susceptibility of neuronal subtypes to teratogenic agents like MAM.