Loeb J M, deTarnowsky J M, Doerschuk S H, Whitson C C
J Pharmacol Exp Ther. 1984 Nov;231(2):281-5.
The mechanism of autoregulation of cardiac cycle length during phasic alterations in perfusion via the sinus node artery is unclear. Inasmuch as transient catecholamine release has been documented during sinus node artery injections, we sought to determine whether autoregulation of cycle length might be related to a beta receptor-mediated process. We used chloralose-anesthetized mongrel dogs. A right thoracotomy was performed, the vagi and sympathetic inputs to the heart were cut and electrograms were recorded from the sinoatrial (SA) node, right atrium, right ventricle and His bundle. The SA node artery was catheterized and distribution verified. Perfusion of normal Tyrode's solution via the SA node artery at 3 ml/min resulted in significant cycle length slowing which was maximal immediately after onset of perfusion. Plots of the derivative of cycle length with respect to time indicated either a monophasic or biphasic pattern of response. Administration of propranolol (2 mg/kg i.v.) resulted in a significant prolongation of control cycle length. Perfusion of normal Tyrode's solution after propranolol resulted in significantly greater degrees of cycle length prolongation (as judged by integration of area under cycle length curves) as well as only monophasic response patterns. These results suggest that infusions of normal Tyrode's solution, via the SA node artery, at physiologic flow rates are accompanied by concurrent catecholamine release throughout the infusion. This catecholamine release may contribute to the homeostatic regulation of cardiac cycle length.
在通过窦房结动脉进行灌注的阶段性改变过程中，心动周期长度的自动调节机制尚不清楚。鉴于在窦房结动脉注射期间已记录到短暂的儿茶酚胺释放，我们试图确定周期长度的自动调节是否可能与β受体介导的过程有关。我们使用了水合氯醛麻醉的杂种犬。进行右胸切开术，切断心脏的迷走神经和交感神经输入，并从窦房（SA）结、右心房、右心室和希氏束记录电描记图。将导管插入窦房结动脉并验证其分布。以3 ml/min的速度通过窦房结动脉灌注正常的台氏液会导致显著的周期长度减慢，在灌注开始后立即达到最大值。周期长度相对于时间的导数图显示出单相或双相反应模式。静脉注射普萘洛尔（2 mg/kg）导致对照周期长度显著延长。普萘洛尔给药后灌注正常的台氏液会导致周期长度延长的程度显著更大（通过周期长度曲线下面积的积分判断），并且仅出现单相反应模式。这些结果表明，以生理流速通过窦房结动脉输注正常的台氏液时，在整个输注过程中会同时释放儿茶酚胺。这种儿茶酚胺释放可能有助于心脏周期长度的稳态调节。
