Hattori Y, Kanno M
Gen Pharmacol. 1984;15(2):91-7. doi: 10.1016/0306-3623(84)90089-2.
Inotropic responses produced by stimulation of alpha-adrenoceptors were compared with those by isoproterenol in the left atria of rats. The negative frequency-force relationship was abolished or attenuated by isoproterenol, but not counteracted by phenylephrine in the presence of sotalol. The positive inotropic effect of phenylephrine was uniquely modulated by reduction in extracellular Ca2+ concentration. Verapamil at 10(-8) M (at which it produces no negative intropic action) depressed only the effect of phenylephrine. Pretreatment with Ca2+-antagonistic cations in low concentrations depressed the effect of phenylephrine without influencing that of isoproterenol.
在大鼠左心房中，比较了刺激α-肾上腺素能受体产生的变力反应与异丙肾上腺素产生的变力反应。异丙肾上腺素消除或减弱了负性频率-力关系，但在索他洛尔存在的情况下，去氧肾上腺素并未抵消这种关系。去氧肾上腺素的正性变力作用仅通过降低细胞外Ca2+浓度而受到独特调节。10(-8) M的维拉帕米（在此浓度下它不产生负性变力作用）仅抑制去氧肾上腺素的作用。低浓度的Ca2+拮抗阳离子预处理可抑制去氧肾上腺素的作用，而不影响异丙肾上腺素的作用。
