[Hemodynamic structure of pressor reactions to vasoactive substances]

In cats, similar changes of the blood pressure had different hemodynamic structures under the influence of catecholamines or angiotensin. Adrenalin was able to evoke a pressor response by means to either caridac or vascular factor. In the former case, the increase in the cardiac output was induced both by an increasing blood flow towards the heart and by an additive outflow of the blood from the minor to the major circulation; in the latter case, the increase in the general peripheral resistance entailed a decrease in the cardiac output in spite of the augmentation of the venous return which determined a delay of the blood in the minor circulation. The latter variant of interrelationships among hemodynamic parameters can occur under the influence of noradrenaline as well. A combined similarly rendered participation of the cardiac and the vascular factors in the increasing the blood pressure occurs under the influence of angiotensin and sometimes of noradrenaline. The participation of cardiac output in the pressor response may depend on hemodynamic shifts in the minor circulation which either limit or facilitate, or leave unchanged the rate of increment of the cardiac output.