Membrane Potentials in the Muscles of the South American Frog, Leptodactylus Ocelatus

Abstract

1. The resting potential of the fibres of the South American frog Leptodactylus ocelatus has been measured using microelectrodes. 2. In 2 mM. potassium Ringer solution values of 85-103 mV. were obtained. The value for a given muscle depends upon the external K concentration and the relation between resting potential and the concentrations of K, Na and Cl in the medium can be fitted to the constant field solution of the diffusion equation. 3. Use of phosphate solutions in place of chloride solutions led to lower resting potentials at a given K concentration, which is understandable since the contribution of Cl ions to the resting potential is not present in the phosphate solution. 4. The action potential was observed. Its rate of fall was less when the positive overshoot was low than when the overshoot was high. 5. Analyses of muscles and plasma were made.