The left ventricular contractility of the rat heart is modulated by changes in flow and <FONT FACE=Symbol>a</font>1-adrenoceptor stimulation

Abstract

a1-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. The contribution of each of these factors to the increase in myocardial performance needs to be clarified. Thus, in the present study we used two protocols: in the first we measured mean arterial pressure, left ventricular pressure and rate of rise of left ventricular pressure development in anesthetized rats (N = 10) submitted to phenylephrine (PE) stimulation before and after propranolol plus atropine treatment. These observations showed that in vivo 1-adrenergic stimulation increases left ventricular-developed pressure (P<0.05) together with arterial blood pressure (P<0.05). In the second protocol, we measured left ventricular isovolumic systolic pressure (ISP) and CPP in Langendorff constant flow-perfused hearts. The hearts (N = 7) were perfused with increasing flow rates under control conditions and PE or PE + nitroprusside (NP). Both CPP and ISP increased (P<0.01) as a function of flow. 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 1-adrenoceptors and increased flow, increased cardiac performance acting simultaneously and synergistically.]]>

Lactate Up-Regulates the Expression of Lactate Oxidation Complex-Related Genes in Left Ventricular Cardiac Tissue of Rats

“…The isolated hearts were prepared as previously described by Vassalo et al [ 13 ] with a few modifications. Briefly, the hearts transferred to the Langendorff apparatus were perfused through aorta under a constant flow (± 9 ml/min.)…”

Bacopa monnieri extract increases rat coronary flow and protects against myocardial ischemia/reperfusion injury

“…However, in the presence of B. monnieri coronary flow was substantially greater than the increased LVDP, which suggests that the vasculature dilated independently of myocardial needs. Nevertheless, there was a slightly increased myocardial contractility with B. monnieri , which might be facilitated by the augmented blood flow as seen in the canine and rat hearts [ 33 , 34 ]. Moreover, the positive ionotropic effect of B. monnieri suggests the extract had no adverse action on the intact myocardium.…”