Kim Y T, Park Y J, Jung S Y, Seo W S, Suh C K
Department of Physiology and Biophysics, College of Medicine, Inha University, 253, Yonghyun-Dong, Nam-Ku, Incheon, 402-751 Korea.
Neuroscience. 2005;131(3):589-99. doi: 10.1016/j.neuroscience.2004.11.045.
Variations in intracellular calcium activity ([Ca2+]i) play crucial roles in information processing in Purkinje neurons such as synaptic plasticity. Although Na+-Ca2+ exchanger (NCX) has been shown to participate in the regulation of homeostasis and secretion in neuronal cells, the physiological role of NCX in Purkinje neurons, such as a role in cerebellar synaptic plasticity, is not well understood. NCX in acutely dissociated rat Purkinje neurons was identified by double staining with anti-calbindin D-28k antibody and anti-NCX antibody. The physiological activity of NCX was examined by measuring transient intracellular Ca2+ changes resulting from the Ca2+ influx via reverse mode of NCX (with 0 mM Na+/2.5 mM Ca2+ solutions) and the efflux via the forward mode of NCX (with 140 mM Na+/0 mM Ca2+ solutions). This transient increase in Ca2+ concentration was not elicited in the cells pretreated with NCX antisense oligodeoxynucleotides. And the Ca2+ influx resulting from the reverse mode of NCX was significantly reduced by 2-[2-[4-(4-nitrobenyloxy) phenyl] ethyl] isothiourea methanesulfonate, while the Ca2+ efflux via forward mode was inhibited by bepridil. The physiological role of NCX in synaptic function was studied by measuring Ca2+ transients induced by alpha-amino-3-hydroxy-5-methyl-4-isoxazolone-propionate (AMPA) receptor activation. This AMPA-evoked response was decreased with the inhibition of NCX forward mode and also, to less degree, with the inhibition of reverse mode. In antisense oligodeoxynucleotides pretreated cells, the AMPA-evoked response was also reduced, as was the case in NCX-inhibitor treated cells. The inhibition of NCX activity had depressant effects on Ca2+ transients induced by AMPA receptor activation. These results suggest that NCX plays a physiological role in modulating the activity of cerebellar Purkinje neurons, such as synaptic plasticity, via interaction with AMPA receptors in Purkinje neurons.
细胞内钙活性（[Ca2+]i）的变化在浦肯野神经元的信息处理（如突触可塑性）中起着关键作用。尽管钠钙交换体（NCX）已被证明参与神经元细胞内稳态和分泌的调节，但NCX在浦肯野神经元中的生理作用，如在小脑突触可塑性中的作用，尚未得到充分了解。通过用抗钙结合蛋白D-28k抗体和抗NCX抗体进行双重染色，鉴定了急性分离的大鼠浦肯野神经元中的NCX。通过测量由NCX反向模式（在0 mM Na+/2.5 mM Ca2+溶液中）的Ca2+内流和正向模式（在140 mM Na+/0 mM Ca2+溶液中）的外流所导致的细胞内Ca2+的瞬时变化，来检测NCX的生理活性。在用NCX反义寡脱氧核苷酸预处理的细胞中，未引发这种Ca2+浓度的瞬时升高。并且，2-[2-[4-(4-硝基苄氧基)苯基]乙基]异硫脲甲磺酸盐可显著降低NCX反向模式导致的Ca2+内流，而苄普地尔可抑制正向模式的Ca2+外流。通过测量由α-氨基-3-羟基-5-甲基-4-异恶唑丙酸（AMPA）受体激活诱导的Ca2+瞬变，研究了NCX在突触功能中的生理作用。随着NCX正向模式的抑制，这种AMPA诱发的反应降低，并且在较小程度上，随着反向模式的抑制也降低。在反义寡脱氧核苷酸预处理的细胞中，AMPA诱发的反应也降低，这与NCX抑制剂处理的细胞情况相同。抑制NCX活性对AMPA受体激活诱导的Ca2+瞬变有抑制作用。这些结果表明，NCX通过与浦肯野神经元中的AMPA受体相互作用，在调节小脑浦肯野神经元的活性（如突触可塑性）中发挥生理作用。
