Na+/Ca2+ exchange and regulation of cytoplasmic concentration of calcium in rat cerebellar neurons treated with glutamate

Abstract

In the present work, the forward and/or reversed Na+/Ca2+ exchange in cerebellar granular cells was suppressed by substitution of Na+o by Li+ before, during, and after exposure to glutamate for varied time and also using the inhibitor KB-R7943 of the reversed exchange. After glutamate challenge for 1 min, Na+o/Li+ substitution did not influence the recovery of low [Ca2+]i in a calcium-free medium. A 1-h incubation with 100 microM glutamate induced in the neurons a biphasic and irreversible [Ca2+]i rise (delayed calcium deregulation (DCD)), enhancement of [Na+]i, and decrease in the mitochondrial potential. If Na+o had been substituted by Li+ before the application of glutamate, i.e. the exchange reversal was suppressed during the exposure to glutamate, the number of cells with DCD was nearly fourfold lowered. However, addition of the Na+/K+-ATPase inhibitor ouabain (0.5 mM) not preventing the exchange reversal also decreased DCD in the presence of glutamate. Both exposures decreased the glutamate-caused loss of intracellular ATP. Glucose deprivation partially abolished protective effects of the Na+o/Li+ substitution and ouabain. KB-R7943 (10 microM) increased 7.4-fold the number of cells with the [Ca2+]i decreased to the basal level after the exposure to glutamate. Thus, reversal of the Na+/Ca2+ exchange reinforced the glutamate-caused perturbations of calcium homeostasis in the neurons and slowed the recovery of the decreased [Ca2+]i in the post-glutamate period. However, for development of DCD, in addition to the exchange reversal, other factors are required, in particular a decrease in the intracellular concentration of ATP.

Neuroprotective Effect of KB-R7943 Against Glutamate Excitotoxicity is Related to Mild Mitochondrial Depolarization

“…replacement decreases cellular 45 Ca 2? accumulation in response to glutamate/ NMDA and induces a significant delay in DCD [39,40]. Therefore, in order to accelerate the onset of DCD, we increased the Ca 2?…”

Scientific Laboratories of the Institute of Pediatrics: Achievements and Prospects

“…Коллектив лаборатории изучал молекулярные механизмы повреждений нейронов при ишемии мозга, эпилепсии, нейродегенеративных заболеваниях избыточным глутаматом. При этом было установлено, что гиперстимуляция рецепторов глутамата является центральным патогенетическим звеном при этих формах патологии мозга [20][21][22]. Впервые была выявлена деполяризация мембраны митохондрий при гиперстимуляции глутаматных рецепторов, эта митохондриальная деполяризация сопровождалась развитием кальциевого плато [23,24].…”