Direct Current-Induced Calcium Trafficking in Different Neuronal Preparations

Figure 2

The accumulation of ⁴⁵Ca²⁺ by the DC-stimulated sciatic nerve in vitro. (a) An experimental setup. The Petri dish (3 cm in diameter) was divided into two parts with partition made of hydrophobic petroleum jelly/silicone oil mixture. There was a stainless steel electrode placed at the bottom of each part (6 × 10 mm). The segment of the sciatic nerve was extended through the partition. The only electrical connection between two parts of the Petri dish was through the sciatic nerve. The electrodes were connected to DC power supply delivering 0.1 mA for 3′. The reference electrode was much closer (approximately 8–10-fold) than in in vivo experiments. Therefore, to compensate for the distance and equalize experimental conditions, the intensity of stimulation for these experiments was adjusted accordingly. ⁴⁵Ca²⁺ was always added to the same part called “inner chamber.” (b) ⁴⁵Ca²⁺ accumulation in the inner and outer segments exposed to either anodal or cathodal stimulation delivered to inner chamber. The anodal DC stimulation induced statistically significant increase in ⁴⁵Ca²⁺ accumulation in the outer segment (, Mann–Whitney U test) and in Ringer’s solution collected from outer chamber (, Mann–Whitney U test). The anodal and cathodal stimulations induced a similar increase in the segment of the nerve located in the inner chamber, although those increases were not statistically significant. Note the increase in the concentration of ⁴⁵Ca²⁺ in the outer chamber (right side of Figure 1(b)). This diagram has two separate scales to express the amount of ⁴⁵Ca²⁺ in the nerve (cpm/mm, left scale) and the concentration of ⁴⁵Ca²⁺ in the Ringers of the outer chamber (cpm/ml, right scale). (c) The total accumulation of ⁴⁵Ca²⁺ in the inner and outer chambers; as compared with control, and as compared with “anode in”; Mann–Whitney U test.

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