A Study of the Effects of the Acute Pulmonary Artery Banding on Baroreflex Regulation of Sympathetic Nerve Activity in Rabbits

Joo, Chan Uhng

Abstract

BACKGROUND
Constriction or banding of the pulmonary artery to create pulmonary artery stenosis is a palliative procedure designed to limit pulmonary blood flow in congenital cardiac malformation with unrestricted left to right shunt. Activation of sensory endings such as the arterial baroreceptors results in an inhibitory endings in the heart. The purpose of this study is to test the hypothesis that acute pulmonary artery constriction(PAC) results in an enhanced cardiopulmonary inhibition of the arterial baroreflex.
METHODS
Baroreflex control of renal sympathetic nerve activity(RSNA) were examined in rabbits before and during reversible PAC. New Zealand white rabbits were instrumented with an occluder around the main pulmonary artery, a right ventricular catheter, femoral artery and venous catheters, and recording electrodes around renal sympathetic nerves. Baroreflex mediated changes in RSNA were monitored during decreases and increases in mean arterial pressure.
RESULTS
Acute PAC produced significant([<0.05) changes in mean arterial pressure(76.3+/-1.9 vs. 59.8+/-3.0mmHg), right ventricular systolic pressure(23.1+/-4.2 vs. 42.3+/-7.4mmHg), and resting RSNA(100 vs. 71+/-6.3%). The effect of acute PAC on the arterial baroreflex was characterized by decreases in RSNA range(103.0+/-1.3 vs. 83.8+/-3.8%) and gain (-3.5+/-0.2 vs. -2.6+/-0.2).
CONCLUSION
Acute PAC significantly attenuates arterial baroreflex control of RSNA in rabbits. The attenuated arterial baroreflex regulation of RSNA may be result of an enhanced inhibitory influence from activated cardiac receptors.