The Movements of Sodium Ions in the Isolated Abdominal Nerve Cord of the Cockroach, Periplaneta Americana

Abstract

1. The rate of loss of sodium ions from the abdominal nerve cord of Periplaneta has been determined by following the decline in radioactivity of ²⁴Na-loaded nerve cords isolated in flowing Ringer solution. 2. In all of the experiments there was an initial rapid exponential decline in radioactivity which eventually gave way to a second slower phase. 3. The initial exponential extrusion of sodium ions was appreciably reduced by the presence of potassium cyanide and 2:4-dinitrophenol. 4. The rate of sodium efflux was not reduced in sodium-free solutions, but was decreased in the absence of external potassium ions. 5. It is concluded that sodium ions are extruded from the nerve cord by a metabolically maintained secretory mechanism which is also associated with the uptake of potassium ions.