Electrophysiological examination of transmitter release in non-quantal form in the mouse diaphragm and the activity of membrane ATP-ase.
The subsynaptic area of mouse diaphragm fibres was hyperpolarized by 1--2 mV during local curarization of the junctional zone in the presence of the reversible anticholinesteraze prostigmine (6 X 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 X 10(-5) M ouabain the hyperpolarization increased to 1.5 +/- 0.25 mV. Removal of potassium ions from the bathing medium also increased curare induced hyperpolarization to 1.80 +/- 0.40 mV. Reactivation of membrane ATP-ase by addition of K+ after a period in K+-free medium reduced the hyperpolarization to zero, where measurements were performed 10--20 min after the readdition. It was concluded that spontaneous non-quantal leakage of acetylcholine occurs at the mouse neuromuscular junction, as it does in the frog (ref. Katz and Miledi 1977). Conditions which block the Na+-K+-dependent ATP-ase of nerve terminals increased the continuous leakage of ACh and activation of the pump decreased it.
D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000818:Animals; D002800:Cholinesterase Inhibitors / Q000494:pharmacology; D003964:Diaphragm / Q000201:enzymology / Q000378:metabolism* / Q000502:physiology; D004594:Electrophysiology; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D009388:Neostigmine / Q000494:pharmacology; D018377:Neurotransmitter Agents / Q000378:metabolism*; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors; D014403:Tubocurarine / Q000494:pharmacology
D002800:Cholinesterase Inhibitors; D018377:Neurotransmitter Agents; D009388:Neostigmine; D010042:Ouabain; D000251:Adenosine Triphosphatases; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium; D014403:Tubocurarine