Figure 6

Sodium chlorate affects morphological and functional maturation of neural precursor cell-derived neurons. (A, B) In order to analyze the neuronal morphology, the βIII-Tubulin immunoreactivity was visualized using diaminobenzidine. In the control situation the neurons often displayed a multipolar morphology with long neurites. Upon NaClO₃ treatment the neurites appeared to be shorter. (C-E) To assess the morphological maturation, the neurite number, the length of the longest neurite and the soma size were measured. The latter two are given in arbitrary units. While the neurite number and the soma size were not altered in the presence of NaClO₃ (n = 6), the mean length of the longest neurite was significantly reduced (n = 6; P <0.05). (F) Whole cell patch-clamp recordings of individual NPC-derived neurons were performed under voltage clamp conditions. To take neuronal subpopulations into account, only neurons exhibiting a triangular soma shape were analyzed. Upon depolarization, the neurons responded with a brief sodium inward current followed by a delayed potassium outward current. The inward component was strongly reduced in the presence of NaClO₃. (G) The determination of the cell capacitance revealed no changes in the overall cell size upon NaClO₃ treatment (n = 5 preparations). (H) Analysis of the two current components expressed as current density clearly showed a reduced sodium current density in the presence of NaClO₃ (n = 5 preparations; P <0.001). In contrast, the potassium current density was not affected (n = 5 preparations). Scale bar: 25 μm.