Temperature alters the inotropic and chronotropic effect of D1-dopamine receptor stimulation in the mammalian atrium

We studied how hypothermia and hyperthermia may change the efficacy and/or potency of dopamine to augment the force of contraction in atria of mice with cardiac overexpression of the human D₁-dopamine receptor (D₁-TG). We measured the force of contraction on paced (1 Hz) left atria and spontaneously beating right atria of these D₁-TG mice in vitro. The intrinsic heart beat in the right atria from D₁-TG mice lowered when we reduced the temperature (24 °C, hypothermia) and elevated when we raised the temperature (42 °C, hyperthermia) in the organ baths. In addition, the efficacy of dopamine (0.001-100 µM) to augment the force of contraction was diminished in the left and right D₁-TG mouse atrial preparations under 24 °C and 42 °C compared to 37 °C in the organ baths. Likewise, the rise in force after dopamine was diminished at 24 °C and 42 °C compared to 37 °C in paced human atrial preparations (HAP) obtained from patients who underwent surgery. In conclusion, the inotropic effects of dopamine in D₁-TG mice and in human atrial preparation via D₁-dopamine receptors, but also the effects of dopamine in D₁-TG mice on the heartbeat, change with ambient temperature.