Chloride-dependent acute excitotoxicity in adult rat retinal ganglion cells

Excitotoxicity-Associated p53 Expression in Adult Rat Retina Is Mediated by Calpain Activity but Not by Cl− Influx

“…DNA fragmentation may become prominent at later periods (9) that are beyond the time scale assessable in our eyecup preparation. Influx of Cl − has been frequently implicated in excitotoxic degeneration of neuronal cells of various regions (10), and our previous study suggested that acute excitotoxic RGC death depends on Cl − influx through niflumic acidsensitive Cl − channels (2). In sharp contrast, we found here that reduction of extracellular Cl − did not prevent kainate-induced p53 expression mediating delayed excitotoxicity in RGCs.…”

“…In vitro experimental systems for evaluation of acute RGC death with propidium iodide staining in our previous study (2) and delayed RGC death with immunohistochemistry for p53 in the present study are useful for investigating the mechanisms of excitotoxicity in the retina and searching for new drugs protecting RGCs.…”

“…The mechanisms of excitotoxicity in RGCs remain controversial, however, due to the lack of suitable in vitro experimental systems for evaluation of RGC death. To circumvent this problem, we have established a novel system for evaluation of RGC death using posterior eyecups prepared from adult rats (2). Using this preparation, we uncovered the dependence of acute excitotoxicity on extracellular Cl − rather than extracellular Ca 2+ (2).…”

“…To circumvent this problem, we have established a novel system for evaluation of RGC death using posterior eyecups prepared from adult rats (2). Using this preparation, we uncovered the dependence of acute excitotoxicity on extracellular Cl − rather than extracellular Ca 2+ (2). However, the proportion of dead RGCs as assessed by propidium iodide staining was at most 15% of the total RGCs at 6 h after treatment with excitotoxins such as N-methyl-D-aspartate (NMDA) and kainate.…”

“…Retrograde labeling of RGCs with fluoro-gold (FG; Fluorochrome, LLC, Denver, CO, USA) was performed on male 7-week-old Sprague-Dawley rats under anesthesia with pentobarbital as described (2). Four days after FG injection, rats were killed by decapitation; and the eyeballs were obtained and transferred into petri dishes containing ice-cold artificial cerebrospinal fluid (aCSF) consisting of 124 mM NaCl, 5 mM KCl, 2 mM MgSO 4 , 2 mM CaCl 2 , 1.25 mM NaH 2 PO 4 , 22 mM NaHCO 3 , and 10 mM glucose.…”