Figure 2.
Voltage-gated sodium channel distribution is rapidly disrupted by hypoperfusion. A, Nav1.6 sodium channels, which outline the node of Ranvier, are normally bounded by the paranodal protein Caspr, as shown in the sham. In response to hypoperfusion, after 3 d and 1 month, the distribution of the Nav1.6 sodium channels is markedly altered and laterally spreads along the axon (corpus callosum). Scale bar, 1 μm. B, There is a significant increase in the length of the Nav1.6 clusters after 3 d of hypoperfusion in the corpus callosum and, after 1 month, in the internal capsule and optic tract. Forty nodes per animal were analyzed and these 240–400 nodes are plotted as cumulative frequency distribution, tabulated as relative frequencies as percentage (two-sample Kolmogorov–Smirnov test). Number of nodes of Ranvier remains unchanged after 3 d or 1 month of hypoperfusion. C, Confocal stack of nodes of Ranvier in the corpus callosum, double-labeled with Nav1.6 and Caspr. Left, Sham; right, 1 month of hypoperfusion. Scale bar, 1 μm. D, Numbers of nodes of Ranvier are not altered in response to hypoperfusion. After 3 d and after 1 month, the number of Nav1.6 immunopositive nodes was not changed between the sham and hypoperfused groups. Analysis was conducted by confocal laser microscopy in the corpus callosum, internal capsule, and optic tract in a 47 × 47 × 5 μm3 confocal stack (Mann–Whitney, two-tailed).