SYSTEMIC BAROREFLEX ALTERATIONS IN PREHEPATIC PORTAL HYPERTENSIVE CONSCIOUS RATS

In portal hypertensive patients and experimental models, hyperdynamic circulatory disturbances associated to a reduced peripheral resistance and an increased cardiac output appeared The aim of this research is the study of the baroreflex system behavior in partially portal vein l igated-portal hypertensive rats.Sham operated rats (S) (n=7) and porta l hypertensive rats (PH) (n=9) were used In anesthetized rats, cathete rs were introduced into a jugular vein for drug injection and into the ventral tail artery to record blood pressure and heart rare. When mts were conscious and moving freely, a bolus injection of phenylephrine hydrochloride (6 mu g/kg) was injected in the vein. A sigmoid curve re lating systolic blood pressure and heart period was dressed. We analyz ed: I) The gain or sensitivity: the slope of the regression line; 2) T he threshold: systolic blood pressure at which the regression begins t o be linear. The results were: mean arterial pressure (mmHg): S=103+/- 7; PH=109+/-3; gain (ms/mmHg): S=1.29+/-0.10; PH=0.62+/-0.04 (p<0.001) ; threshold (mmHg): S=145+/-7; PH=146+/-4.The baroreceptor reflex sens itivity was significantly decreased. No differences appeared in the me an arterial pressure and in the reflex threshold It is suggested that portal hypertension induces alterations in baroreflex regulation of ar terial blood pressure.