Chronic cholestasis in rats induces anhedonia and a loss of social interest

Central fatigue commonly occurs in patients with primary biliary cirrhosis (PBC) and correlates closely with depression, and cholestatic rats exhibit central fatigue. Therefore, we undertook a series of experiments in both rats with cholestasis caused by bile duct, resection (BDR) and sham-resected controls (IS days after surgery) to determine if experimental cholestasis is associated with symptoms of depression that can be modeled in rats, namely anhedonia (loss of pleasure) and the loss of social interest. BDR rats exhibited significant anhedonia compared with sham controls as indicated by a loss in their preference for consuming a saccharin solution, a highly desirable drink for rats. Furthermore, social interest was examined by determining the time BDR or sham rats spent investigating a juvenile rat in an open-field apparatus compared with the time spent on nonsocial behaviors. BDR rats exhibited significantly reduced time spent in social investigation and significantly more time in nonsocial behaviors than did sham rats. Major depression in humans is often associated with elevated circulating glucocorticoid levels and impaired glucocorticoid feedback. Therefore, we measured these parameters in BDR and ham rats and found a striking elevation in circulating glucocorticoid levels in BDR compared with sham animals. However, elevated circulating glucocorticoid levels in BDR rats suppressed normally in response to exogenous dexamethasone, indicating intact glucocorticoid feedback control at the pituitary level in BDR rats. In summary, we have identified behaviors in cholestatic rats that are consistent with those seen in depression.