Susceptibilities to and mechanisms of excitotoxic cell death of adult mouse inner retinal neurons in dissociated culture.
OBJECTIVE
To explore the susceptibilities of adult retinal neurons in dissociated culture to treatments with excitotoxic agonists and the mechanisms of the resultant retinal cell death.


METHODS
C57B6 mice were used. Retinas were removed, dissociated, plated on a polylysine/laminin substrate, and maintained in vitro for 5 to 7 days. Excitotoxic agonists (glutamate, N-methyl-D-aspartate [NMDA], or kainic acid [KA]) were added for 30 minutes or 24 hours, sometimes in the presence of modified extracellular ion concentrations or potential blocking agents. The next day, cells were fixed and immunocytochemically stained to identify ganglion and amacrine cells. Surviving cells were counted.


RESULTS
Ganglion cells from adult mouse retinas were much less susceptible to excitotoxic death than those prepared from neonatal retinas. Adult amacrine cells were killed by KA, NMDA, or glutamate. Experiments with selective blockers demonstrated that KA killed through AMPA (alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid) receptors, whereas NMDA and glutamate exerted toxicity through a combination of AMPA and NMDA receptors. The KA-induced death of amacrine cells was not mediated by chloride ions. Removal of extracellular sodium, however, completely prevented the amacrine cell death, and removal of extracellular calcium prevented approximately 70% of the death. The path of calcium entry was investigated. Experiments with selective blockers indicated that the lethal calcium entry was via reverse operation of a sodium-calcium exchanger.


CONCLUSIONS
There is a profound developmental regulation in the sensitivity of retina ganglion cells to excitotoxic insults. Excessive intracellular sodium and calcium are the proximal causes of amacrine cell death. The pathologic calcium entry is dependent on the sodium overload, which then drives a sodium-calcium exchanger to take up calcium.
Luo
Xianmin
X
Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, St. Louis, MO 63110, USA.
Baba
Akemichi
A
Matsuda
Toshio
T
Romano
Carmelo
C
D025042:Amacrine Cells / Q000187:drug effects / Q000502:physiology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D004351:Drug Resistance; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D018698:Glutamic Acid / Q000494:pharmacology; D007150:Immunohistochemistry; D007608:Kainic Acid / Q000494:pharmacology; D051379:Mice; D008810:Mice, Inbred C57BL; D016202:N-Methylaspartate / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects* / Q000502:physiology*; D009498:Neurotoxins / Q000494:pharmacology*; D018091:Receptors, AMPA / Q000502:physiology; D016194:Receptors, N-Methyl-D-Aspartate / Q000502:physiology; D012160:Retina / Q000166:cytology*; D012165:Retinal Ganglion Cells / Q000187:drug effects; D012964:Sodium / Q000378:metabolism; D019831:Sodium-Calcium Exchanger / Q000378:metabolism
D018690:Excitatory Amino Acid Agonists; D009498:Neurotoxins; D018091:Receptors, AMPA; D016194:Receptors, N-Methyl-D-Aspartate; D019831:Sodium-Calcium Exchanger; D018698:Glutamic Acid; D016202:N-Methylaspartate; D012964:Sodium; D007608:Kainic Acid; D002118:Calcium