Negative Inotropic Effects of Class I Antiarrhythmics on Guinea Pig Ventricular Myocardium: Correlation with L-Type Ca2+ Channel Blockade.

The negative inotropic effects of nine Vaughan Williams class I antiarrhythmic drugs were examined in guinea pig ventricular tissue preparations. The drugs decreased the contractile force of papillary muscles with different potencies: the potency order was propafenone > aprindine > cibenzoline > flecainide > ranolazine > disopyramide > pilsicainide > mexiletine > GS-458967. The potency of drugs correlated with the reported IC50 values to block the L-type Ca2+ channel rather than the Na+ channel. The effects of drugs were roughly the same when examined under a high extracellular K+ solution, which inactivates the Na+ channel. Furthermore, the attenuation of the extracellular Ca2+-induced positive inotropy was strong with propafenone, moderate with cibenzoline, and weak with pilsicainide. These results indicate that the negative inotropic effects of class I antiarrhythmic drugs can be largely explained by their blockade of the L-type Ca2+ channel.

Magnetic Weyl Semimetal in K_{2}Mn_{3}(AsO_{4})_{3} with the Minimum Number of Weyl Points.

The "hydrogen atom" of magnetic Weyl semimetals, with the minimum number of Weyl points, has received growing attention recently due to the possible presence of Weyl-related phenomena. Here, we report a nontrivial electronic structure of the ferromagnetic alluaudite-type compound K_{2}Mn_{3}(AsO_{4})_{3}. It exhibits only a pair of Weyl points constrained in the z direction by the twofold rotation symmetry, leading to extremely long Fermi arc surface states. In addition, the study of its low-energy effective model results in the discovery of various topological superconducting states, such as the hydrogen atom of a Weyl superconductor. Our Letter provides a feasible platform to explore the intrinsic properties related to Weyl points, and the related device applications.