[Adaptive capabilities of the "hypokinetic" heart of the rat to a resistance load and the role of nervous regulation].

Adaptation of the heart of hypokinetic rats to sustained afterload and the role of nervous regulation in this process were investigated. The experimental rats were subdivided into four groups: 1) control, 2) hypokinesia for 64 days, 3) coarctation of aorta for 4 days, and 4) hypokinesia for 60 days plus coarctation of aorta for 4 days. It was found that the rates of contraction and relaxation of the heart increased by 22 = 51% in the Group 2 rats and decreased by 32 = 40% in the Group 3 rats as compared to the controls. Coarctation of aorta that followed 60-day hypokinesia (Group 4) reduced the increased parameters to the control level. After heart denervation (vagotomy and drug desympathization) all the rats showed depression of the contractile parameters to a varying degree: Group 2 rats exhibited the lowest degree of depression. It can be concluded that cardiac resistance of the hypokinetic rats to afterload is higher than in the intact rats with coarctation of aorta; on the other hand, afterload reduces the hypokinesia-induced increase in the contractility function, making it close to the control level. In addition to the nervous influences (sympathetic), intracardiac factors play an important role in the mechanisms of adaptation of the heart to hypokinesia and of the hypokinetic heart to afterload.