Summary
The effect of varying the potassium ion concentration on autonomic neuro-muscular transmission was studied in the vas deferens of the mouse. The smooth muscle cells had resting membrane potentials in normal solution of about 75 mV. The relationship between the membrane potential and the external potassium concentration was close to that predicted by the Nernst equation for external potassium concentrations above 20 mM. The relationship followed the trend predicted by the Goldman equation. The time of decay of the excitatory junction potential (EJP) in response to nervous stimulation decreased to one quarter when the potassium concentration was increased from 0 to 5 times that in normal solution. The transmission delay at the autonomic junction did not change, and the rise time of the EJP decreased only slightly, with increased external potassium concentration. The maximal amplitude of the EJP decreased with increased external potassium. Miniature EJPs (MEJPs) occurred spontaneously and had the same time course in each concentration of external potassium. In potassium-free solution spontaneous potentials, which were similar in time course to EJPs in the same solution, were also observed. It is concluded that the repolarizing phase of the EJP in normal solution is probably determined by the electrical properties of the smooth muscle.
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Furness, J.B. The effect of external potassium ion concentration on autonomic neuro-muscular transmission. Pflugers Arch. 317, 310–326 (1970). https://doi.org/10.1007/BF00586580
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DOI: https://doi.org/10.1007/BF00586580