Arterial and cardiopulmonary baroreflex control of renal nerve activity in cirrhosis

Cirrhotic rats (common bile duct ligation; CBDL) have increased efferent renal sympathetic nerve activity (ERSNA), which contributes significantly to the observed renal sodium and water retention and edema formation. Basal ERSNA is increased and fails to suppress normally during intravenous isotonic saline volume expansion. Arterial and cardiopulmonary baroreflex control of ERSNA in CBDL and control (CTR) rats was examined. CBDL rats exhibited hyperdynamic circulation with increased cardiac index and decreased total peripheral resistance index and arterial pressure compared with CTR rats. Increases in left ventricular end-diastolic pressure (LVEDP) produced by volume expansion increased cardiac index normally in CBDL rats. The maximal gain of aortic baroreflex control of ERSNA was similar in CBDL and CTR rats. In CBDL rats, during decreased arterial pressure, there was a decreased range of the central component, which accounted for the decreased range of the overall aortic baroreflex, with the range of the afferent component being normal. For cardiopulmonary baroreflex control of ERSNA, the LVEDP threshold was increased and the gain was decreased in CBDL compared with CTR rats; this was due to an increased LVEDP threshold and a diminished gain of the afferent component while the central portion of the reflex was normal. These abnormalities in the cardiopulmonary baroreflex account for the attenuated decrease in ERSNA in CBDL compared with CTR rats during volume expansion. In CBDL rats, attenuation of cardiopulmonary baroreflex control of ERSNA contributes to both the increased basal ERSNA and its failure to normally suppress during volume expansion.