Influence of veratrine on the muscle contracting action of potassium

1. Veratrine greatly sensitizes the action of potassium ions on frog's rectus muscle. Quinine inhibits the sensitizing action of veratrine. 2. Perfusate of the preparation from the stimulated veratrinized hind limbs evokes a contraction of the veratrinized test muscle. 3. The other purfusates of the preparations perfused with Ringer's solution or with veratrine-Ringer's solution do not affect the test muscle. But a similar contraction is observable if potassium chloride of a certain strength, is added to the perfusates. 4. It can be shown that the chemical agent causing the muscular contraction is potassium ions, 5. The above experimental results may be wholly explained by the assumption that veratrine increases the permeability of muscle cell membrane to potassium ions.