Membrane Potentials in Cell‐free Preparations from Guinea Pig Cerebral Cortex: Effect of Depolarizing Agents and Cyclic Nucleotides

Abstract

The distribution of [3H]triphenylmethylphosphonium ion between the medium and vesicular entities was examined in a cell-free, particulate preparation from guinea pig cerebral cortex. This distribution followed the Nernst relationship with regard to the external potassium ion concentration and, in physiological media, indicated the maintenance of a mean trans-membrane potential ranging from -58 to -78 mV. The neurotoxins batrachotoxin, veratridine and grayanotoxin I partially depolarized the preparation. Tetrodotoxin blocked the depolarization by batrachotoxin, veratridine and grayanotoxin I. The depolarization by these neurotoxins was potentiated by the presence of anemone toxin II and presumably reflected the response of vesicular components of neuronal origin. An additional potassium-sensitive depolarization probably represented the response of vesicular components of glial origin with an apparent transmembrane potential of -8 to -35 mV. No correlation could be demonstrated between changes in transmembrane potential and stimulation of cAMP generation by a variety of agents in this preparation.