Effect of temperature on isoprenaline- and barium-induced slow action potentials in guinea-pig ventricular strips

Abstract

1. 1. The effect of variation in temperature (37-32 and 27°C) on electrical and mechanical activity of depolarized and isoprenaline- or barium-reactivated guinea pig ventricular strips was studied. 2. 2. Lowering the temperature brings a marked prolongation of isoprenaline-induced slow action potentials. In addition the maximal rate of depolarization was strongly reduced at lower temperatures. These effects were observed at an extracellular Ca 2+ concentration of either 0.9 or 2.5 mM. The accompanying mechanical activities was significantly increased by reduction in temperature. 3. 3. Barium-induced slow action potentials were similarly affected by temperature variations. 4. 4. These observations suggest that hypothermia exert a sort of calcium antagonistic action probably coupled to a reduction of repolarizing outward potassium currents.