Comparative Actions of 1,10-Phenanthroline and Quinidine on Normal and Fibrillating Isolated Atria. ∗

Summary

1. A method of inducing fibrillation in isolated rabbit atria was explored. Atrial fibrillation can be readily produced and maintained under the conditions described by Holland and Burn(2). The method is improved here by the use of much lower concentration of acetylcholine. 2. 1,10-Phenanthroline is as effective as quinidine in stopping induced fibrillation in isolated rabbit atria. 3. 1,10-Phenanthroline, like quinidine, reduces the maximal following rate of isolated rabbit atria, but to a lesser extent. 4. The lowering of maximal following rate by 1,10-Phenanthroline and quinidine can be lessened by reduction of potassium in the medium. 5. At comparable concentrations, 1,10-Phenanthroline does not affect the intrinsic sinus rate of isolated rabbit atria, while quinidine reduces the intrinsic rate markedly. 6. 1,10-Phenanthroline, like quinidine, produces distinct reduction of the rate of depolarization and repolarization of the action potential of the rat atria.