Differential temperature-dependency of electrophysiological and inotropic actions of nifedipine, verapamil and cinnarizine in K +-depolarized ventricular myocardium

Abstract

1. 1. Temperature dependency (in the range 27–37°C) of inotropic and electrophysiological effects of equieffective (EC 30 at 37°C) concentrations of nifedipine, verapamil and cinnarizine was assessed in potassium depolarized isoprenaline-reactivated guinea-pig ventricular strips. 2. 2. Lowering temperature greatly enhanced nifedipine inhibition of (a) maximal rate of depolarization ( V max) of slow action potentials and (b) amplitude of contractions. 3. 3. Electrophysiological and inotropic actions of verapamil was virtually unaffected by temperature changes. 4. 4. Negative inotropic action of cinnarizine was greater at 37°C than at lower temperature. At 37°C, but not at 32°C, cinnarizine reduced V max of slow action potentials.