The quantitation of Kv1.1 potassium channel localization demonstrates that the channels are concentrated in the CNS and PNS juxtaparanodal regions in the wild-type (+/+) but not in the galatolipid-deficient (−/−) mice. In the CNS of the −/− animals, potassium channels are often not detected (ND), diffusely distributed throughout the internode, or restricted to the paranode but rarely limited to the juxtaparanodal region. In the mutant PNS, the channels were predominately concentrated in the paranodal region. For the CNS, 128 nodes from five wild-type mice and 120 nodes from four mutant mice were analyzed. For the PNS, 26 nodes from three mice were analyzed for both groups.