Influence of the extracellular potassium environment on neurite growth in sensory neurons, spinal cord neurons and sympathetic neurons

Abstract

The influence of the extracellular potassium concentration ([K +] o) on neurite growth in rat sensory neurons, spinal cord neurons and sympathetic neurons was investigated. Experiments carried out in 3-compartment culture dishes showed that although neurites from sensory and spinal cord neurons were capable of growing in both 5 mM [K +] o and 20 mM [K +] o, they were virtually unable to grow from a region of 5 mM [K +] o into a region of 20 mM [K +] o. Neurites from sympathetic neurons behaved similarly although [K −] o exceeding 20 mM was required to exclude sympathetic neurites. We suggest the possibility of a negative chemotaxis to [K +] o by growth cones in these neurons. Neurite regeneration following axotomy in sensory neurons was partially inhibited distal to a proximodistal increase in [K +] o. The nature of this inhibition was somewhat different from that described previously in sympathetic neurons. The possibility is raised that [K +] o plays a role in the development of the nervous system.