Márquez M T, Mikulić L E, Aramendía P
Methods Find Exp Clin Pharmacol. 1981 Sep-Oct;3(5):283-9.
In the isolated rat atria the effects of phenylephrine (alpha-agonist) and isoproterenol (beta-agonist) on the contractile force and heart rate were studied either in presence or not of alpha- and/or beta-blockade. Phentolamine 10(-6) M and propranolol 10(-8) M were used as alpha- and beta-antagonists, respectively. The chronotropic dose-response curves were made in both spontaneously beating atria while inotropic effects were derived from left atria driven at 1 Hz, 5 msec and voltage about 20 percent above threshold. Both agonists induced an inotropic effect that could be significantly blocked by phentolamine, propranolol and both antagonists given together. The chronotropic dose-response curve of isoproterenol (pD2 = 10.70 +/- 0.11) was blocked by phentolamine (pD2 = 9.27 +/- 0.08, p less than 0.001) and propranolol (pD2 = 9.21 +/- 0.19, p less than 0.001). Contrarily, pentolamine was unable to shift to the right the chronotropic dose-response curve for phenylephrine (pD2 = 6.48 +/- 0.07 and 6.63 +/- 0.10, respectively). This action of phenylephrine on the heart rate was significantly blocked by propranolol (pD2 = 6.21 +/- 0.13, p less than 0.05) and by propranolol plus phentolamine (pD2 = 6.07 +/- 0.04, p less than 0.001). From the present results it is concluded that in the rat's atrial myocardium there exist alpha- and beta-adrenoceptors mediating the positive inotropic effect of isoproterenol and phenylephrine. Yet, the chronotropic action seems to behave in a different way: while isoproterenol triggered either type of receptors; phenylephrine is only mediated by beta-adrenoceptors.U
在离体大鼠心房中，研究了去氧肾上腺素（α受体激动剂）和异丙肾上腺素（β受体激动剂）在存在或不存在α和/或β受体阻滞剂的情况下对收缩力和心率的影响。分别使用10⁻⁶ M的酚妥拉明和10⁻⁸ M的普萘洛尔作为α和β受体拮抗剂。变时剂量反应曲线在自发搏动的心房中绘制，而变力作用则来自于以1 Hz、5毫秒和高于阈值约20%的电压驱动的左心房。两种激动剂均诱导出变力作用，酚妥拉明、普萘洛尔以及两者联合使用均可显著阻断该作用。异丙肾上腺素的变时剂量反应曲线（pD2 = 10.70 ± 0.11）被酚妥拉明（pD2 = 9.27 ± 0.08，p < 0.001）和普萘洛尔（pD2 = 9.21 ± 0.19，p < 0.001）阻断。相反，酚妥拉明无法使去氧肾上腺素的变时剂量反应曲线右移（分别为pD2 = 6.48 ± 0.07和6.63 ± 0.10）。去氧肾上腺素对心率的这种作用被普萘洛尔（pD2 = 6.21 ± 0.13，p < 0.05）以及普萘洛尔加酚妥拉明（pD2 = 6.07 ± 0.04，p < 0.
