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 cultu re to external application of adenosine 5'-triphosphate (ATP). ATP ind uced 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 re versibly 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 s equence through the anion channel: SCN- > I- > Br- approximate to Cl- > aspartate > isethionate. I-ATP did not appear to be dependent on int racellular calcium, as inclusion or omission of calcium chelator (BAPT A, 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 r elative 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.