Inotropic and chronotropic responses of the in vivo denervated dog myocardium to dobutamine

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Abstract
The inotropic and chronotropic responses to dobutamine (DBA) and isoprenaline (ISO) were examined in 8 chloralose anesthetised dogs. Following acute cardiac denervation, heart rate (HR) and contractility (dP/dtmax), measured at a fixed paced atrial rate, were recorded during i.v. infusion of incremental doses of DBA and ISO. Both DBA and ISO elicited increases in HR and dP/ktmax. The increases in dP/dtmax for a 1 beat/min increase in HR was 102.0 .+-. 10.6 mm Hg/s (1 mm Hg (0.degree. C) = 133.322 pascal), during DBA infusion, and 61.5 .+-. 8.4 mm Hg/s during ISO infusion. The relatively greater inotropic effect of DBA in comparison with ISO was the result of an augmentation of its inotropic activity. DBA infusion was accompanied by a significant increase in mean aortic pressure at all doses examined. An increase in afterload may account for part of the increased inotropic response to DBA.

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