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Baroreceptor Reflex (baroreceptor + reflex)
Selected AbstractsChronic inhibition of standing behaviour alters baroreceptor reflex function in ratsACTA PHYSIOLOGICA, Issue 3 2009H. Waki Abstract Aim:, To investigate whether daily orthostatic stress during development is an important factor affecting arterial baroreceptor reflex function, we examined the effect of chronic inhibition of upright standing behaviour on the baroreceptor reflex function in rats. Methods:, Upright standing behaviour was chronically inhibited during the developmental period between 3 and 8 weeks of age in Sprague,Dawley rats and heart rate (HR) and aortic nerve activity in response to increased and decreased mean arterial pressure (MAP) was measured after the treatment period. Results:, The baroreceptor cardiac gain in the rats grown without standing behaviour was significantly lower than the control rats grown in a normal commercial cage (1.0 ± 0.1 beats min,1 mmHg,1 vs. 1.6 ± 0.2 beatsmin,1 mmHg,1, P < 0.05). The range of HR change in the MAP,HR functional curve was also lowered by chronic inhibition of orthostatic behaviour (56.2 ± 5.9 beats min,1) compared with that of the control rats (76.8 ± 6.9 beats min,1, P < 0.05). However the aortic afferent function remained normal after the treatment period, indicating that the attenuated baroreceptor reflex function may be due to other mechanisms involving functional alterations in the cardiovascular centres, efferents and/or peripheral organs. Body weight and adrenal weight were not affected by the inhibition of orthostatic behaviour, suggesting that the animals were not exposed to specific stress by this treatment. Conclusion:, These results indicate that active haemodynamic changes induced by orthostatic behaviour are an important factor for setting the basal level of reflex function during development. Moreover, our experimental model may be useful for studying mechanisms of attenuated baroreceptor reflex observed after exposure to a chronic inactive condition. [source] Aldosterone receptor antagonists , how cardiovascular actions may explain their beneficial effects in heart failureJOURNAL OF VETERINARY PHARMACOLOGY & THERAPEUTICS, Issue 2 2010P. OVAERT Ovaert, P., Elliott, J., Bernay, F., Guillot, E., Bardon, T. Aldosterone receptor antagonists , how cardiovascular actions may explain their beneficial effects in heart failure. J. vet. Pharmacol. Therap.33, 109,117. Historically, aldosterone receptor antagonists (ARA) have been classified as ,potassium sparing diuretics'. However, the positive effect of spironolactone, the most extensively studied ARA, on morbidity and mortality observed in humans suffering cardiac insufficiency could not be explained by the renal effect of the drug alone, and a pivotal clinical study has led to extensive research. Many experimental studies have demonstrated that ARA have previously unexpected beneficial effects on the cardiovascular system including reduction in remodelling of the vascular smooth muscle cells and myocytes and improvement of endothelial cell dysfunction in heart failure. These effects improve vascular compliance and slow down the progression of left ventricular dysfunction and end-organ damage. Furthermore, aldosterone receptor blockade also restores the baroreceptor reflex, improving heart rate variability in heart failure in humans. Some of these effects have been demonstrated in dog models of cardiac disease and so justified further investigation of the potential benefit of ARA in dogs with congestive heart failure (CHF). Positive effects of spironolactone on morbidity and mortality appear to have been seen in studies conducted in dogs suffering from naturally occurring CHF. In addition, eplerenone has been shown to have benefits in canine models of heart failure. The precise mechanisms by which ARA produce these beneficial effects in dogs remain to be determined but this group of drugs clearly provide therapeutic actions out-with their diuretic effects. [source] IDENTIFICATION OF BLOOD PRESSURE CONTROL MECHANISMS BY POWER SPECTRAL ANALYSISCLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 4 2007Harald M Stauss SUMMARY 1Blood pressure and organ perfusion are controlled by a variety of cardiovascular control systems, such as the baroreceptor reflex and the renin,angiotensin system (RAS), and by local vascular mechanisms, such as shear stress-induced release of nitric oxide (NO) from the endothelium and the myogenic vascular response. Deviations in arterial blood pressure from its set point activate these mechanisms in an attempt to restore blood pressure and/or secure organ perfusion. However, the response times at which different cardiovascular mechanisms operate differ considerably (e.g. blood pressure control by the RAS is slower than blood pressure control via the baroreceptor reflex). 2Owing to these different response times, some cardiovascular control systems affect blood pressure more rapidly and others more slowly. Thus, identifying the frequency components of blood pressure variability (BPV) by power spectral analysis can potentially provide important information on individual blood pressure control mechanisms. 3Evidence is presented that the RAS, catecholamines, endothelial-derived NO and myogenic vascular function affect BPV at very low frequencies (0.02,0.2 Hz) and that low-frequency (LF) BPV (0.2,0.6 Hz) is affected by sympathetic modulation of vascular tone and endothelial-derived NO in rats. In humans, LF BPV (0.075,0.15 Hz) is affected by sympathetic modulation of vascular tone and myogenic vascular function. The impact of the RAS and endothelial-derived NO on BPV in humans requires further investigation. 4In conclusion, power spectral analysis is a powerful diagnostic tool that allows identification of pathophysiological mechanisms contributing to cardiovascular diseases, such as hypertension, heart failure and stroke, because it can separate slow from fast cardiovascular control mechanisms. The limitation that some cardiovascular control mechanisms affect the same frequency components of BPV requires the combination of blood pressure spectral analysis with other techniques. [source] REFLEXLY EVOKED COACTIVATION OF CARDIAC VAGAL AND SYMPATHETIC MOTOR OUTFLOWS: OBSERVATIONS AND FUNCTIONAL IMPLICATIONSCLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 12 2006Julian FR Paton SUMMARY 1The purpose of the present review is to highlight the pattern of activity in the parasympathetic and sympathetic nerves innervating the heart during their reflex activation. 2We describe the well-known reciprocal control of cardiac vagal and sympathetic activity during the baroreceptor reflex, but point out that this appears to be the exception rather than the rule and that many other reflexes reviewed herein (e.g. peripheral chemoreceptor, nociceptor, diving response and oculocardiac) involve simultaneous coactivation of both autonomic limbs. 3The heart rate response during simultaneous activation of cardiac autonomic outflows is unpredictable because it does not simply reflect the summation of opposing influences. Indeed, it can result in bradycardia (peripheral chemoreceptor, diving and corneal), tachycardia (nociceptor) and, in some circumstances, can predispose to malignant arrhythmias. 4We propose that this cardiac autonomic coactivation may allow greater cardiac output during bradycardia (increased ventricular filling time and stronger contraction) than activation of the sympathetic limb alone. This may be important when pumping blood into a constricted vascular tree, such as is the case during the peripheral chemoreceptor reflex and the diving response. [source] | ||||||||||