Effects of chronic bile-duct ligation on the baroreceptor reflex in dogs

The purpose of the present experiments was to examine the effects of chronic bile-duct ligation (CBDL) on the baroreceptor reflex system. The open-loop gain (G) of the baroreceptor reflex system and pressor response to noradrenaline were measured in seven dogs with CBDL for 4 to 6 weeks, and the data were compared with those of seven control dogs. The liver function of the CBDL-dogs was significantly impaired. G was assessed as (delta API/delta APS)-1, where delta API and delta APS represent the immediate and steady-state decreases in arterial pressure at the aortic arch following a fast step-wise reduction in blood volume. The value of G was 8.8 +/- 0.9 (mean +/- SE) in the control-group and 5.3 +/- 2.1 in the CBDL-group (p less than 0.05). The maximum increase in arterial pressure in response to a bolus injection of noradrenaline (0.5 micrograms/kg i.v.) was 29.3 +/- 4.4 mm Hg in the control-group and 19.7 +/- 1.6 mm Hg in the CBDL-group (p less than 0.05). These findings suggest that CBDL leads to a decrease in responsiveness of the vascular smooth muscle to noradrenaline which in turn results in a decrease in open-loop gain of the baroreceptor reflex system.