Leier C V, Nelson S, Magorien R D, Boudoulas H, Gibb L, Unverferth D V
J Lab Clin Med. 1983 Jun;101(6):955-63.
Six normal male human subjects underwent two 72 hr infusions of saline (control) and butopamine, a beta-adrenergic agonist with strong positive chronotropic properties, in order to determine the chronotropic responsiveness of the human heart after sustained chronotropic stimulation. Chronotropic responsiveness was assessed by heart rate responses to intravenous isoproterenol and bicycle ergometry before and serially over 50 hr after discontinuation of the infusions. Chronotropic responsiveness to isoproterenol and exercise was reduced significantly in the butopamine group compared to control; this blunted chronotropic effect persisted beyond 48 hr. Positive inotropic responsiveness, assessed by echocardiography and systolic time intervals, was reduced modestly for the butopamine-treated group up to 24 hr after infusion. Although the precise mechanisms are not fully elucidated, continuous chronotropic stimulation of the human heart with the beta 1 agonist, butopamine, elicits a significant reduction in the heart rate response to isoproterenol and exercise challenges. In addition, the degree and time course of suppression of the chronotropic vs. inotropic responsiveness are disparate.
六名正常男性受试者接受了两次为期72小时的生理盐水（对照）和布托巴胺输注，布托巴胺是一种具有强烈正性变时作用的β肾上腺素能激动剂，目的是确定持续变时刺激后人心脏的变时反应性。在输注停止前及停止后连续50小时，通过静脉注射异丙肾上腺素和自行车测力计引起的心率反应来评估变时反应性。与对照组相比，布托巴胺组对异丙肾上腺素和运动的变时反应性显著降低；这种变时作用减弱持续超过48小时。通过超声心动图和收缩期时间间期评估的正性肌力反应性，在布托巴胺治疗组输注后长达24小时内略有降低。尽管确切机制尚未完全阐明，但用β1激动剂布托巴胺持续对人心脏进行变时刺激，会使心脏对异丙肾上腺素和运动刺激的心率反应显著降低。此外，变时反应性与正性肌力反应性抑制的程度和时间过程是不同的。
