Reflex Vascular Responses to Changes in Left Ventricular Pressure in Anaesthetized Dogs

Abstract

SUMMARYIn dogs anaesthetized with chloralose, changes in left ventricular systolic pressure were induced using a preparation in which the pressure changes did not distend the aortic arch and in which left atrial and carotid sinus pressures were held constant. The systemic circulation was perfused at constant flow and drained from the venae cavae at constant pressure. An increase in left ventricular systolic pressure caused reflex dilatation of systemic resistance and capacitance vessels as indicated by decreases in arterial perfusion pressure and venous outflow. Responses were obtained when ventricular systolic pressure changed between 16 and 28 kPa (120-210 mHg). Responses to changes in ventricular pressure were reduced when the carotid sinuses were perfused at high pressures. These results indicate that changes in pressure in the left ventricle result in reflex changes in vascular resistance and capacitance and that responses are obtained to changes in ventricular pressure over a physiological range.

Convergence properties of solitary tract neurones driven synaptically by cardiac vagal afferents in the mouse

“…This information may then be relayed to distinct outflows either controlling cardiac vagal motor or sympathetic pre-motor neurones, for example. With regard to reflexes evoked from cardiac receptors, stimulation of chemically sensitive cardiac receptors produced bradycardiaÏdepressor in both mouse (Paton & Butcher, 1997) and dog (McGregor et al 1986;Tutt et al 1988). Since the common reflex response of both chemically sensitive cardiac receptors and chemoreceptors is a vagally mediated bradycardia, an NTS neurone receiving convergence from these afferents may, therefore, indicate a role in controlling cardiac vagal motor neurones.…”

“…Since the common reflex response of both chemically sensitive cardiac receptors and chemoreceptors is a vagally mediated bradycardia, an NTS neurone receiving convergence from these afferents may, therefore, indicate a role in controlling cardiac vagal motor neurones. By analogy, since stimulation of mechanically sensitive cardiac receptors produced a depressor effect but failed to produce a bradycardia consistently (Tutt et al 1988;Paton & Butcher, 1997), NTS neurones excited by these cardiac receptors and baroreceptors may act to depress sympathetic activity. Since pulse-modulated activity was only seen in cardiac vagal afferents during high and maintained levels of LVEDP (e.g.…”

The absence of cardiovascular and respiratory responses to changes in right ventricular pressure in anaesthetized dogs.

“…In this respect the right ventricle differs from the left, in which changes in systolic pressure result in dilatation of resistance vessels (Challenger et al 1987;Tutt et al 1988) and reductions in respiratory activity (Crisp et al 1987). The preparation that we used in this study was adapted from that which we used to study responses to stimulation of left ventricular receptors (Crisp et al 1987) and was designed to localize a mechanical stimulus as precisely as possible to the right ventricle.…”

“…There is now adequate evidence that mechanical stimulation of nerves ending in the left ventricle, by moderate increases in ventricular systolic pressure, results in reflex dilatation of both resistance and capacitance vessels (Challenger, McGregor & Hainsworth, 1987;Tutt, McGregor & Hainsworth, 1988) and a reflex reduction of respiratory activity (Crisp, Hainsworth, McGregor & Tutt, 1987.) However, it is still unknown whether changes in pressure localized to the right ventricle result in reflex cardiovascular or respiratory responses.…”

“…The carotid arteries were cannulated and perfused at constant pressures as previously described (Tutt et al 1988). …”