Membrane potentials in cell-free preparations from guinea pig cerebral cortex: effect of depolarizing agents and cyclic nucleotides.

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 gray-anotoxin 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 cyclic AMP generation by a variety of agents in this preparation.