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Published on: March 18, 2021
Organization of cortico-cortical associative projections in a rat model of microgyria
S Giannetti1, P Gaglini, F Di Rocco
1Institute of Anatomy, Catholic University Medical School, Rome, Italy.
Abstract:
Microgyria was experimentally induced by focal freezing lesions of the frontal cortex in newborn rats. Adult microgyric animals received cortical injections of biotinylated dextran amine combined with NMDA, in order to obtain a Golgi-like retrograde labeling of cortico-cortical association neurons. Injections were performed either rostrally or caudally to the microgyric lesion. Results demonstrate that long-range association projections traveling across the zone of the microgyric lesion arise mainly from infragranular layers. In normal animals the same projections originate both from supragranular and infragranular layers. The analysis of single basal dendrites of layer 2/3 in microgyric animals demonstrates a simplified branching pattern, with a number of end points lower than in control animals. Potential implications for microgyria-associated epilepsy are discussed.
Insights
This study reveals altered neuronal connections in microgyria, a condition affecting brain development. Long-range projections in affected rats primarily originate from deeper layers, differing from normal brain development.
Area of Science:
- Neuroscience
- Developmental Neuroscience
- Neurobiology
Background:
- Microgyria is a developmental brain disorder characterized by an increased number of cortical folds.
- It is often associated with neurological deficits, including epilepsy.
- Understanding altered neuronal circuitry in microgyria is crucial for developing therapeutic strategies.
Purpose of the Study:
- To investigate the impact of experimentally induced microgyria on cortico-cortical association neuron projections.
- To analyze dendritic morphology in microgyric rats compared to control animals.
Main Methods:
- Microgyria was induced in newborn rats using focal freezing lesions of the frontal cortex.
- Retrograde labeling of cortico-cortical neurons was achieved using biotinylated dextran amine and NMDA injections in adult microgyric rats.
- Dendritic branching patterns of layer 2/3 neurons were analyzed.
Main Results:
- Long-range association projections traversing the microgyric lesion site predominantly originated from infragranular layers in affected rats.
- In contrast, normal animals showed projections originating from both supragranular and infragranular layers.
- Microgyric animals exhibited a simplified dendritic branching pattern in layer 2/3 neurons with fewer endpoints.
Conclusions:
- Experimentally induced microgyria alters the laminar origin of long-range cortico-cortical projections.
- Dendritic simplification in superficial cortical layers is a feature of this microgyria model.
- These findings may have implications for understanding epilepsy associated with microgyria.
