Nuclear disintegration as a leading step of glutamate excitotoxicity in brain neurons.

Abstract

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.

• Authors: J Ikeda, S Terakawa, S Murota, I Morita, K Hirakawa
• Journal: Journal of neuroscience research (J Neurosci Res) Vol. 43 Issue 5 Pg. 613-22 (Mar 01 1996) ISSN: 0360-4012 [Print] United States
• PMID: 8833096 (Publication Type: Journal Article)

Chemical References

• Glutamic Acid
• Calcium

Topics

• Animals
• Brain (cytology, drug effects)
• Calcium (metabolism)
• Cell Nucleus (drug effects, physiology)
• DNA Fragmentation
• Glutamic Acid (poisoning)
• Intracellular Membranes (metabolism)
• Neurons (cytology, drug effects)
• Osmolar Concentration
• Rats (embryology)
• Time Factors