MODIFICATION OF IONIC CURRENTS UNDERLYING ACTION-POTENTIALS IN MOUSE NERVE-TERMINALS BY THE THIOL-OXIDIZING AGENT DIAMIDE

The effect of diamide, a thiol-oxidizing agent, was tested using elect rophysiological techniques to determine whether its ability to alter n euromuscular transmission in vitro could be attributed to alterations of ion channels controlling neuronal excitability and/or acetylcholine release. In mouse triangularis sterni preparations, diamide transient ly increased the evoked release of acetylcholine and then blocked rele ase. Extracellular recording of perineural waveforms associated with n euronal action potentials at motor nerve terminals showed that diamide reduced the waveforms associated with the delayed rectifier K+ curren t, a Ca2+ current and a Ca2+-activated K+ current (I-K,I-Ca). Inhibiti on of quantal transmitter release was not associated with failure of a ction potentials to invade nerve terminals. Thus, diamide modifies the ionic currents underlying the nerve terminal action potential, some o f these changes probably account for the complex effects of diamide on quantal transmission.