ELECTROPHYSIOLOGICAL EXAMINATION OF TRANSMITTER RELEASE IN NON-QUANTAL FORM IN MOUSE DIAPHRAGM AND ACTIVITY OF MEMBRANE ATPASE

  • 1 January 1978
    • journal article
    • research article
    • Vol. 27  (5) , 449-455
Abstract
The subsynaptic area of mouse diaphragm fibers was hyperpolarized by 1-2 mV during local curarization of the junctional zone with the reversible anticholinesterase prostigmine (6 .times. 10-6 M), or after treatment of the muscle with organophosphate cholinesterase inhibitor Soman. In a solution containing 5 mM K+ the mean hyperpolarization was 1.1 .+-. 0.27 mV at mean resting potential -70 mV. After adding 2 .times. 10-5 M ouabain the hyperpolarization increased to 1.5 .+-. 0.25 mV. Removal of K ions from the bathing medium also increased curare-induced hyperpolarization to 1.80 .+-. 0.40 mV. Reactivation of membrane ATPase by adding K+ after a period in K+-free medium reduced the hyperpolarization to 0, when measurements were performed 10-20 min after the readdition. Spontaneous non-quantal leakage of acetylcholine [ACh] occurs at the mouse neuromuscular junction, as it does in the frog. Conditions which block the Na+-K+-dependent ATPase of nerve terminals increased the continuous leakage of ACh and activation of the pump decreased it.