Köhr G, Lambert C E, Mody I
Department of Neurology and Neurological Sciences, Stanford University Medical Center, CA 94305.
Exp Brain Res. 1991;85(3):543-51. doi: 10.1007/BF00231738.
Nerve cells that lack the cytoplasmic Ca2+ binding protein Calbindin-D28K (CaBP) appear to be selectively vulnerable to Ca(2+)-related injury consistent with a postulated intraneuronal Ca(2+)-buffering role of CaBP. We have confirmed the selective loss of CaBP from the dentate gyrus during kindling-induced epilepsy in acutely dissociated granule cells (GCs) from kindled rats. Immunohistochemically stained kindled neurons showed a significant loss of CaBP when compared to controls (p less than 0.001; ANOVA). The Ca(2+)-buffering role of CaBP was assessed in acutely dissociated control and kindled GCs by examining a physiological process highly sensitive to intracellular Ca(2+)-buffering: the Ca(2+)-dependent inactivation of high-voltage activated (HVA or L-type) Ca2+ currents in the absence (or presence) of exogenous Ca(2+)-chelators. Whole-cell patch clamp recordings in kindled GCs demonstrated a markedly enhanced Ca(2+)-dependent inactivation of Ca(2+)-currents. After brief conditioning Ca2+ currents, in the absence of an exogenous intraneuronal Ca(2+)-chelator, subsequent test Ca2+ currents were inactivated by 58.3% in kindled GCs, a significant increase from the 37.4% inactivation observed in control GCs (p less than 0.005; ANOVA). The differential Ca2+ current decay and Ca(2+)-dependent inactivation were prevented in both control and kindled GCs upon loading the neurons with the exogenous Ca(2+)-chelator BAPTA. These experiments demonstrate a high correlation between the loss of CaBP and changes in Ca2+ current inactivation and are consistent with the hypothesis that CaBP contributes to the physiological Ca(2+)-buffering in mammalian neurons.
缺乏细胞质钙结合蛋白钙结合蛋白-D28K（CaBP）的神经细胞似乎对与钙相关的损伤具有选择性易感性，这与CaBP假定的神经元内钙缓冲作用一致。我们已经证实在点燃大鼠急性分离的颗粒细胞（GCs）中，在点燃诱导的癫痫发作期间齿状回中CaBP会选择性丧失。与对照组相比，免疫组织化学染色的点燃神经元显示CaBP显著丧失（p<0.001；方差分析）。通过检查对细胞内钙缓冲高度敏感的生理过程，在急性分离的对照和点燃的GCs中评估CaBP的钙缓冲作用：在不存在（或存在）外源钙螯合剂的情况下，高压激活（HVA或L型）钙电流的钙依赖性失活。点燃的GCs中的全细胞膜片钳记录显示钙电流的钙依赖性失活明显增强。在短暂的预处理钙电流后，在不存在外源神经元内钙螯合剂的情况下，点燃的GCs中随后的测试钙电流失活了58.3%，与对照GCs中观察到的37.4%失活相比有显著增加（p<0.005；方差分析）。在用外源钙螯合剂BAPTA加载神经元后，对照和点燃的GCs中钙电流衰减和钙依赖性失活的差异均被阻止。这些实验证明了CaBP丧失与钙电流失活变化之间的高度相关性，并且与CaBP有助于哺乳动物神经元生理钙缓冲的假设一致。
