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Electroconvulsive Seizures in Rats and Fractionation of Their Hippocampi to Examine Seizure-induced Changes in Postsynaptic Density Proteins
Published on: August 15, 2017
Changes in microtubule-associated protein-2 (MAP2) expression during development and after status epilepticus in the
Niina S Jalava1, Francisco R Lopez-Picon, Tiina-Kaisa Kukko-Lukjanov
1Department of Pharmacology, Drug Development, and Therapeutics, Institute of Biomedicine, University of Turku, Itäinen Pitkäkatu 4B, FIN-20014 Turku, Finland.
Abstract:
In this study, we analyzed the spatiotemporal expression patterns of the high-molecular weight (MAP2a and b) and low-molecular weight (MAP2c and d) cytoskeletal microtubule-associated protein-2 (MAP2) isoforms with Western blotting, and the cellular localization of the high-molecular weight MAP2 isoforms with immunocytochemistry in the hippocampi of 1- to 21-day-old rats. Moreover, the temporal profile (from 30 min to 1 week) of MAP2 isoform reactivity to kainic acid-induced status epilepticus was studied in P9 rats. During development, the expression of the high-molecular weight MAP2 isoforms significantly increased, while the low-molecular weight isoforms decreased, the most prominent changes occurring during the second postnatal week. This developmental increase in the high-molecular weight MAP2 expression was also confirmed with immunocytochemistry, which showed increased immunoreactivity, particularly in the molecular layers of the dentate gyrus, and in CA1 and CA3 stratum radiatum. In 9-day-old rats, status epilepticus resulted in a rapid transient increase (about 210%) in the high-molecular weight MAP2 expression, without any effect on the low-molecular weight MAP2. Moreover, disturbed dendritic structure in the CA1 and CA3 stratum radiatum was manifested as formation of varicosities 3h after the kainic acid treatment. The strictly developmentally regulated MAP2 isoform expression suggests different functional roles for these proteins during the postnatal development in the rat hippocampus. Moreover, high-molecular weight MAP2s may play a role in nerve cell survival during cell stress.
Insights
High-molecular weight microtubule-associated protein-2 (MAP2) isoforms increase during rat hippocampal development, while low-molecular weight isoforms decrease. Stress, like seizures, rapidly boosts high-molecular weight MAP2 expression.
Area of Science:
- Neuroscience
- Developmental Biology
- Cell Biology
Background:
- Microtubule-associated protein-2 (MAP2) is crucial for neuronal structure and function.
- MAP2 exists in high-molecular weight (MAP2a, MAP2b) and low-molecular weight (MAP2c, MAP2d) isoforms with distinct developmental expression patterns.
- Understanding MAP2 isoform dynamics is key to comprehending hippocampal development and response to injury.
Purpose of the Study:
- To investigate the spatiotemporal expression and localization of MAP2 isoforms during rat hippocampal development.
- To examine the temporal response of MAP2 isoforms to kainic acid-induced status epilepticus in developing rats.
- To elucidate the functional roles of different MAP2 isoforms in neuronal development and stress response.
Main Methods:
- Western blotting to analyze MAP2 isoform expression levels.
- Immunocytochemistry to determine the cellular localization of high-molecular weight MAP2 isoforms.
- Kainic acid-induced status epilepticus model in P9 rats to study acute stress response.
Main Results:
- High-molecular weight MAP2 isoforms significantly increased, while low-molecular weight isoforms decreased during postnatal development (1-21 days), with major changes in the second week.
- Immunocytochemistry confirmed increased high-molecular weight MAP2 immunoreactivity in the dentate gyrus and CA1/CA3 stratum radiatum.
- Status epilepticus in P9 rats caused a rapid, transient ~210% increase in high-molecular weight MAP2 expression without affecting low-molecular weight isoforms; dendritic varicosities formed in CA1/CA3 stratum radiatum within 3 hours.
Conclusions:
- MAP2 isoform expression is strictly developmentally regulated in the rat hippocampus, suggesting distinct functional roles.
- High-molecular weight MAP2 isoforms may play a protective role in neuronal survival during cellular stress.
- The rapid upregulation of high-molecular weight MAP2 following seizure induction highlights its involvement in acute neuronal stress responses.
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