Effect of temperature on isoprenaline- and barium-induced slow action potentials in guinea-pig ventricular strips.
The effect of variation in temperature (37-32 and 27 degrees C) on electrical and mechanical activity of depolarized and isoprenaline- or barium-reactivated guinea pig ventricular strips was studied. 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 Ca2+ concentration of either 0.9 or 2.5 mM. The accompanying mechanical activities was significantly increased by reduction in temperature. Barium-induced slow action potentials were similarly affected by temperature variations. These observations suggest that hypothermia exert a sort of calcium antagonistic action probably coupled to a reduction of repolarizing outward potassium currents.
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D001464:Barium / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology; D006168:Guinea Pigs; D006321:Heart / Q000187:drug effects* / Q000502:physiology; D006352:Heart Ventricles; D066298:In Vitro Techniques; D007473:Ion Channels / Q000187:drug effects; D007545:Isoproterenol / Q000494:pharmacology*; D009200:Myocardial Contraction / Q000187:drug effects; D013696:Temperature
D007473:Ion Channels; D001464:Barium; D007545:Isoproterenol; D002118:Calcium