The study examined the effects of α1A-adrenoceptor stimulation on chronotropic function of Langendorff-perfused isolated heart ex vivo and on cardiac chronotropy in vivo in 7-day-old rats. α1A-Adrenergic receptor agonist A-61603 reduced heart chronotropy only in the whole organism. No chronotropic effects of selective stimulation of α1A-adrenergic receptors on isolated hearts were observed in ex vivo experiments. These findings suggest that α1A-adrenergic receptors are not implicated in HR regulation in newborn rats. Bradycardia induced by activation of these receptors in vivo is most likely associated with reflex influences on the heart and changes in the vascular tone in the whole organism.

中文翻译：

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α1A-肾上腺素能受体刺激对新生大鼠体内和体外心脏作用的比较分析

该研究检查了 α1A-肾上腺素能受体刺激对离体 Langendorff 灌注离体心脏的变时功能和 7 日龄大鼠体内心脏变时功能的影响。α1A-肾上腺素能受体激动剂 A-61603 仅在整个生物体中降低心脏变时性。在离体实验中未观察到选择性刺激 α1A-肾上腺素能受体对离体心脏的变时作用。这些发现表明α1A-肾上腺素能受体与新生大鼠的心率调节无关。由体内这些受体激活引起的心动过缓最有可能与对心脏的反射影响和整个生物体中血管张力的变化有关。