抄録
1. By the use of small strips excised from the inner wall of the ventricle of Dolabella, effects of some cations on the potassium and caffeine contractures, in addition to the relation between the membrane potential and the height of potassium contracture, were examined.
2. The relation between the logarithm of external potassium concentration and the membrane potential was linear in high potassium concentration, but the membrane depolarized in potassium-free solution.
3. In a high potassium concentration the height of spontaneous contractions reduced, accompanying reductions in the amplitude and duration of the action potential.
4. Potassium contractures were induced in the solution containing more than 40 mM of potassium chloride, and the relation between potassium concentration and the height of contracture was similar to that in vertebrate muscles.
5. While no contracture was induced in calcium-free potassium solutions, caffeine contracture was induced in calcium-free solutions.
6. Antagonism between sodium and calcium in the potassium contracture was not so remarkable as expected from the ratio of [Ca]/[Na]2 in the external fluid, while there was a noticeable antagonism between calcium and magnesium.
