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Nuclear disintegration as a leading step of glutamate excitotoxicity in brain neurons
Author(s) -
Ikeda J.,
Terakawa S.,
Murota S.,
Morita I.,
Hirakawa K.
Publication year - 1996
Publication title -
journal of neuroscience research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.72
H-Index - 160
eISSN - 1097-4547
pISSN - 0360-4012
DOI - 10.1002/(sici)1097-4547(19960301)43:5<613::aid-jnr11>3.0.co;2-1
Subject(s) - excitotoxicity , glutamate receptor , nmda receptor , microbiology and biotechnology , kainic acid , neuron , chemistry , apoptosis , glutamatergic , biophysics , biology , biochemistry , neuroscience , receptor
Recent studies on ischemic brain disease in vivo and glutamate excitotoxicity in vitro suggest that apoptosis may play a role in excitotoxic neuronal death. To examine the possible involvement of apoptosis in glutamate excitotoxicity, we studied an early process of morphological changes in rat cortical neurons exposed to 1 mM glutamate. Observations under Nomarski optics combined with a digital image processor revealed a rapid change in the nucleus followed by a cellular swelling. The nucleus increased in granularity and swelled in 5 min, then became liquefied in 30 min. The cell body swelled slowly in 15–45 min. These changes could be prevented by treatment of the neuron with MK‐801 (dizocilpine maleate), a blocker of N‐methyl‐D‐aspartate (NMDA) receptor‐coupled ion channel. However, treatment of the neurons with N G ‐nitro‐ L ‐arginine (N‐NORG), a nitric oxide synthase inhibitor, had no significant effect. Use of the in situ end‐labeling technique for the demonstration of free 3′‐hydroxyl ends revealed that DNA fragmentation took place within 1 hr after glutamate exposure. A change in intracellular Ca 2+ concentration was examined with fluo‐3 under a confocal laser microscope. Application of 1 mM glutamate induced rapid Ca transients in the nucleus as well as in the cytoplasm. Both of these Ca responses were blocked by MK‐801. These results indicate that glutamate excitotoxicity in the brain neuron does not fulfill morphological criteria of apoptosis, but suggest that the nuclear disintegration associated with DNA fragmentation is involved as a leading step in glutamate excitotoxicity. © 1996 Wiley‐Liss, Inc.