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Updated: May 14, 2026
Electroconvulsive Seizures in Rats and Fractionation of Their Hippocampi to Examine Seizure-induced Changes in Postsynaptic Density Proteins
Published on: August 15, 2017
Regulation of ERK1/2 mitogen-activated protein kinase by NMDA-receptor-induced seizure activity in cortical slices
Yoko Yamagata1, Koichi Kaneko, Daisuke Kase
1Department of Information Physiology, National Institute for Physiological Sciences, Myodaiji, Okazaki 444-8787, Japan. yamagata@nips.ac.jp
Abstract:
Extracellular signal-regulated kinase 1/2 (ERK1/2) that belongs to a subfamily of mitogen-activated protein kinases (MAPKs) plays diverse roles in the central nervous system. Activation of ERK1/2 has been observed in various types of neuronal excitation, including seizure activity in vivo and in vitro, as well as in NMDA-receptor (NMDA-R)-dependent long-term potentiation in the hippocampus. On the other hand, recent studies in cultured neurons have shown that NMDA-R stimulation could result in either ERK1/2 activation or non-activation, depending on the pharmacological manipulations. To assess NMDA-R-dependent regulation of ERK1/2 activity in vivo, here we examined the effect of NMDA-R-induced seizure activity on ERK1/2 activation by using rat cortical slice preparations. NMDA-R-dependent seizure activity introduced by Mg2+ -free condition did not cause ERK1/2 activation. On the other hand, when picrotoxin was added to concurrently suppress GABAA-receptor-mediated inhibition, profound ERK1/2 activation occurred, which was accompanied by strong phospho-ERK1/2-staining in the superficial and deep cortical layer neurons. In this case, prolonged membrane depolarization and enhanced burst action potential firings, both of which were much greater than those in Mg2+ -free condition alone, were observed. Differential ERK1/2 activation was supported by the concurrent selective increase in phosphorylation of a substrate protein, phospho-site 4/5 of synapsin I. These results indicate that NMDA-R activation through a release from Mg2+ -blockade, which accompanies enhancement of both excitatory and inhibitory synaptic transmission, was not enough, but concurrent suppression of GABAergic inhibition, which leads to a selective increase in excitatory synaptic transmission, was necessary for robust ERK1/2 activation to occur within the cortical network.
Insights
NMDA-receptor (NMDA-R) activation alone does not trigger ERK1/2 activation in rat cortical slices. Suppressing GABAergic inhibition is necessary for robust extracellular signal-regulated kinase 1/2 (ERK1/2) activation during NMDA-R-induced seizures.
Area of Science:
- Neuroscience
- Cellular signaling
- Molecular biology
Background:
- Extracellular signal-regulated kinase 1/2 (ERK1/2), a mitogen-activated protein kinase (MAPK), has critical roles in the central nervous system.
- ERK1/2 activation is linked to neuronal excitation, including seizures and NMDA-receptor (NMDA-R)-dependent long-term potentiation.
- Previous studies in cultured neurons showed variable ERK1/2 responses to NMDA-R stimulation based on pharmacological conditions.
Purpose of the Study:
- To investigate the in vivo regulation of ERK1/2 activity by NMDA-R-induced seizures in rat cortical slices.
- To determine the specific conditions required for NMDA-R-dependent ERK1/2 activation within the cortical network.
Main Methods:
- Utilized rat cortical slice preparations to study neuronal activity and signaling pathways.
- Induced seizure activity using NMDA-receptor (NMDA-R) activation under Mg2+-free conditions.
- Administered picrotoxin to block GABAA-receptor-mediated inhibition.
- Assessed ERK1/2 activation via phospho-ERK1/2 staining and phosphorylation of synapsin I.
Main Results:
- NMDA-R-dependent seizure activity in Mg2+-free conditions did not induce ERK1/2 activation.
- Concurrent suppression of GABAA-receptor-mediated inhibition with picrotoxin led to profound ERK1/2 activation.
- This robust activation correlated with increased membrane depolarization, enhanced burst firing, and synapsin I phosphorylation.
- Phospho-ERK1/2 staining was prominent in superficial and deep cortical layer neurons.
Conclusions:
- NMDA-R activation alone, even with enhanced synaptic transmission, is insufficient for robust ERK1/2 activation in cortical networks.
- Suppression of GABAergic inhibition is a critical requirement for significant ERK1/2 activation during NMDA-R-induced seizure activity.
- These findings highlight the complex interplay between excitatory and inhibitory neurotransmission in regulating intracellular signaling pathways like ERK1/2.
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