Brazilian journal of medical and biological research = Revista brasileira de pesquisas médicas e biológicas
-
Braz. J. Med. Biol. Res. · Oct 1998
The left ventricular contractility of the rat heart is modulated by changes in flow and alpha 1-adrenoceptor stimulation.
Myocardial contractility depends on several mechanisms such as coronary perfusion pressure (CPP) and flow as well as on alpha 1-adrenoceptor stimulation. Both effects occur during the sympathetic stimulation mediated by norepinephrine. Norepinephrine increases force development in the heart and produces vasoconstriction increasing arterial pressure and, in turn, CPP. ⋯ CPP changes were not affected by drug treatment but ISP increased (P < 0.01). The largest ISP increase was obtained with PE + NP treatment (P < 0.01). The results suggest that both mechanisms, i.e., direct stimulation of myocardial alpha 1-adrenoceptors and increased flow, increased cardiac performance acting simultaneously and synergistically.