Hashimoto H, Nakashima M, Sugino N
Br J Pharmacol. 1983 Jun;79(2):499-507. doi: 10.1111/j.1476-5381.1983.tb11024.x.
The age-dependent differences in the involvement of alpha-adrenoceptors in the positive inotropic effect of phenylephrine (Phe) were examined in isolated atria of male Wistar rats 6 weeks (6W), 10 weeks and 7 months (7M) of age. The maximal increase in tension development induced by Phe increased with age, whereas the EC50 values for the positive inotropic effect of Phe did not change with age. The inhibitory effect of phentolamine on the response to Phe increased with age. Propranolol caused only slight inhibition of the effect of Phe in both 6W and 7M rats, and the EC50 values for Phe in the presence of propranolol did not change significantly with age. The EC50 values for isoprenaline and 5-hydroxytryptamine in 7M rats were higher than those in 6W rats. In 7M rats, the duration of the tension development was only slightly affected by Phe in the presence or absence of propranolol, but it was markedly decreased by Phe in the presence of phentolamine. The dose-response curve for Phe was markedly shifted to the left by papaverine in 6W rats, but slightly in 7M rats. The dose-response curve for isoprenaline was markedly shifted to the left by papaverine in both groups. These results are consistent with effects of Phe being mediated by both alpha- and beta-adrenoceptors in both 6W and 7M rats, but there is a shift in the balance from rather more beta-receptors in the young animals to more alpha-receptors in the adults.
在6周龄（6W）、10周龄和7月龄（7M）的雄性Wistar大鼠离体心房中，研究了α-肾上腺素受体参与去氧肾上腺素（Phe）正性肌力作用的年龄依赖性差异。Phe诱导的张力发展最大增加随年龄增加，而Phe正性肌力作用的EC50值不随年龄变化。酚妥拉明对Phe反应的抑制作用随年龄增加。普萘洛尔对6W和7M大鼠的Phe作用仅产生轻微抑制，且在普萘洛尔存在下Phe的EC50值不随年龄显著变化。7M大鼠中异丙肾上腺素和5-羟色胺的EC50值高于6W大鼠。在7M大鼠中，无论有无普萘洛尔，Phe对张力发展持续时间的影响都很小，但在酚妥拉明存在下Phe会使其明显缩短。在6W大鼠中，罂粟碱使Phe的剂量-反应曲线明显左移，但在7M大鼠中仅轻微左移。两组中罂粟碱均使异丙肾上腺素的剂量-反应曲线明显左移。这些结果与6W和7M大鼠中Phe的作用均由α-和β-肾上腺素受体介导一致，但平衡发生了变化，从幼龄动物中β-受体相对较多转变为成年动物中α-受体相对较多。
