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Development of N-methyl-D-aspartate excitotoxicity in cultured hippocampal neurons
C Peterson1, J H Neal, C W Cotman
1Department of Psychobiology, University of California, Irvine 92717.
Abstract:
Immature hippocampal neurons (E-18) were maintained in defined medium for up to 3 weeks and their susceptibility to N-methyl-D-aspartic acid (NMDA)-induced cell death was studied at various days in vitro. Upon acute exposure to NMDA (5 min), hippocampal neurons in vitro (8-12 days after plating) showed cell body swelling and dendritic degeneration that preceded cell death 24 h later. NMDA-induced neurodegeneration could be prevented by MK-801 treatment but not by tetrodotoxin. In contrast, immature (5-7 days old) neurons were unaltered by exposure to 500 microM NMDA for either 5 min or 24 h. One explanation for the resistance of immature neurons to glutamate neurotoxicity may be related to maturation of the NMDA receptor complex. Glutamate binding to the NMDA receptor in vivo increased from 14.6 +/- 1.6% (0 day) to 55.2 +/- 4.5% (day 7), 79 +/- 4.9% (day 14), 93.8 +/- 2.8% (day 21) until it reached the adult Sprague-Dawley value of 100 +/- 0.8% (day 90).
Insights
Immature neurons are resistant to N-methyl-D-aspartic acid (NMDA) excitotoxicity. This resistance is linked to the maturation of the NMDA receptor complex during neuronal development.
Area of Science:
- Neuroscience
- Cell Biology
- Developmental Biology
Background:
- Hippocampal neurons are crucial for learning and memory.
- Excitotoxicity, mediated by glutamate receptor overactivation, contributes to neuronal damage in various neurological conditions.
- Understanding the developmental trajectory of neuronal vulnerability is essential for targeted therapeutic interventions.
Purpose of the Study:
- To investigate the susceptibility of immature and mature hippocampal neurons to N-methyl-D-aspartic acid (NMDA)-induced cell death in vitro.
- To explore the role of NMDA receptor maturation in determining neuronal resistance to excitotoxicity.
Main Methods:
- Primary hippocampal neuron cultures were established from embryonic day 18 (E-18) rats.
- Neurons were maintained in vitro for up to 3 weeks.
- Exposure to NMDA was performed at various days in vitro, followed by assessment of cell death and morphological changes.
- The effect of MK-801 and tetrodotoxin on NMDA-induced neurotoxicity was evaluated.
- Glutamate binding to NMDA receptors was quantified in vivo at different developmental stages.
Main Results:
- Mature hippocampal neurons (8-12 days in vitro) exhibited significant cell body swelling and dendritic degeneration upon acute NMDA exposure, preceding cell death.
- NMDA-induced neurodegeneration in mature neurons was preventable by MK-801 but not tetrodotoxin.
- Immature neurons (5-7 days in vitro) showed resistance to NMDA exposure.
- In vivo, glutamate binding to the NMDA receptor increased progressively from embryonic stages to adulthood.
Conclusions:
- Immature hippocampal neurons are inherently resistant to NMDA-induced excitotoxicity.
- Neuronal resistance to NMDA is associated with the developmental maturation of the NMDA receptor complex.
- These findings highlight the critical role of receptor maturation in shaping neuronal vulnerability during development.