Recovery of pressor response to norepinephrine following relief of the obstructed common bile duct in the rat

Abstract

Jaundice caused by common bile duct (CBD) obstruction is associated with a blunted pressor response to norepinephrine (NE). We studied the rate and extent of recovery of the pressor response in the rat following relief of the obstruction. Three groups of male Wistar rats underwent CBD ligation. In the first and second group blood pressure measurements were obtained at 72 and 144h after CBD ligation, respectively. In the third group pressure measurements were recorded 72 h after the relief of a 72-h obstruction. A fourth group served as control, and measurements were obtained 72h after a sham operation. In all four groups measurements included basal blood pressure and pressure change following escalating doses of NE, ranging from 0.5 to 10μg/kg. Basal blood pressure was similar in all four groups. In the control group the change of blood pressure was 23.4%±6.7% in response to the lowest dose of NE, and 83.5%±24.9% in response to the highest dose. A blunted pressor response to NE was recorded in all three groups with CBD obstruction. The duration of CBD ligation (72 or 144h) did not affect this blunded response. Re-establishment of bile flow for 72h made only a slight improvement in the response to NE. Obstruction of the CBD was associated with hyperbilirubinemia which disappeared following the re-anastomosis of the CBD to the duodenum. This most significant decrease in serum bilirubin was not associated with a similar improvement in pressor response to NE. We conclude that in the rat CBD obstruction is associated with a blunted pressor response to NE, that relief of CBD obstruction for 72h is insufficient to abolish this response, and that there is no full correlation between serum bilirubin and pressor response.