NA-K-ACTIVATED ATPASE AND THE RELEASE OF ACETYLCHOLINE AND NORADRENALINE

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  • 1 January 1982
    • journal article
    • research article
    • Vol. 78  (4) , 399-406
Abstract
Different experimental conditions that inhibit Na-K-activated ATPase, an enzyme present in the neuronal membranes, promote transmitter release (ACh [acetylcholine], NA [norepinephrine], etc.) from different tissues, simply by making the membrane leaky. Under physiological conditions, Ca entering the cell transiently inhibits membrane ATPase, resulting in a transient change in membrane permeability and a subsequent release of transmitter. When membrane ATPase inhibitor was used, 1 part of the release proved to be Ca-independent. The voltage and Ca-dependent link of transmitter release can be bypassed by direct membrane ATPase inhibitors (ouabain). Neurochemical and electrophysiological evidence was obtained on mouse diaphragm that most of the released ACh is cytoplasmic and Na-K ATPase inhibition is responsible for its release. The stimulation of membrane ATPase (by switching off K and its readmission) results in an inhibition of both ACh and NA release evoked by axonal stimulation. In those cases where the varicose axon terminals do not make synaptic contact, the transmitter released from the cytoplasmic pool contributes to the transmission, since during diffusion (sometimes few thousand nm) transmitter of different origins becomes mixed up.