ATP ACTIVATES CATIONIC AND ANIONIC CONDUCTANCES IN SCHWANN-CELLS CULTURED FROM DORSAL-ROOT GANGLIA OF THE MOUSE

The whole-cell configuration of the patch-clamp technique was used to study membrane responses of mouse Schwann cells in organotypique culture to external application of adenosine 5'-triphosphate (ATP). ATP induced an inward current (I-ATP) which caused a membrane depolarization. I-ATP was dose dependent with a K-d of 8.4 mM. ATP analogues had the following relative agonist potency:ATP > ADP approximate to alpha-beta methylene ATP. Neither AMP nor adenosine were effective. I-ATP was reversibly reduced by suramin, a P-2 purinoceptor antagonist. Alteration of ionic gradients showed that ATP activated simultaneously cationic (potassium and calcium) and anionic (chloride) conductances. Values of the reversal potentials to ATP suggested the following permeability sequence through the anion channel: SCN- > I- > Br- approximate to Cl- > aspartate > isethionate. I-ATP did not appear to be dependent on intracellular calcium, as inclusion or omission of calcium chelator (BAPTA, 10 mM) in the pipette solution had no effect on I-ATP. The observed ATP response resembles a P-2-mediated response in its kinetics, its relative agonist potency and its blockade by suramin, but differs from known ones by its requirements for high concentrations of ATP and the activation of a cationic as well as an anionic conductance.