Cytoskeleton mediates inhibition of the fast Na+ current in respiratory brainstem neurons during hypoxia

Whole-cell Na+ currents (I-Na) were recorded in inspiratory neurons in a medullary slice preparation from neonatal mouse that contains the functional respiratory network. Hypoxia and metabolic poisoning with KCN rapidly inhibited I-Na by reducing the number of Na+ channels available for opening during depolarization. Application of agents specific for G-proteins, protein kinase C and A, intracellular Ca2+ and pH did not prevent the hypoxic inhibition of I-Na. The effects of hypo-osmolarity and hypoxia were additive, whereas hyperosmolarity partially prevented a subsequent hypoxic inhibition of I-Na. Cytochalasin B and colchicine decreased, and taxol or phalloidin increased I-Na and reduced its hypoxic inhibition. We conclude that cytoskeleton rearrangements during hypoxia are responsible for suppression of a fast I-Na in brainstem respiratory neurons, which could be mediated by the uncoupling of channel inactivation gates from cytoskeletal elements.