Influence of temperature on isometric contractions of rabbit atria during inotropic interventions

Inotropic effects on strips of left atria promoted by 1-epinephrine, increase in frequency, post-extrasystolic potentiation, and by increase in extracellular calcium concentration were studied at 28 C and 36 C. The results show that at lower temperature the resulting changes in temporal parameters (activation time, deactivation time and duration above 10% of maximum force) are greater than those at the higher temperature. AT 36 C inotropic interventions have more prominent effects on the tension development and its first derivative, while changes in temporal parameters become less conspicuous. It is concluded that the inotropic interventions regulate the strength of contraction more effectively at 36 C and the temporal aspects of contraction more effectively at 28 C.