Altered axonal expression of 23Na channels in MS. Sections of postmortem spinal cord white matter from control (A and B) and MS (C–L) patients, immunostained to show Nav1.6 (red), Nav1.2 (red), Caspr (integral constituent of paranodal junctions-green), and neurofilaments (blue). In control white matter (A) and in normal-appearing white matter in MS tissue (C), Nav1.6 is localized at nodes of Ranvier whereas Nav1.2 is not detectable (B and D). Within MS plaques, continuous Nav1.6 (E) and Nav1.2 (F) immunostaining are present; in some instances bounded by Caspr (G-H). Colocalization of Nav1.6 (I) and Nav1.2 (J) with neurofilament immunostaining (K and L; blue) confirms the axonal identity of these profiles. Reproduced from Craner et al.2004 Copyright (2004) National Academy of Sciences, U.S.A.