Resumo

Hepatic Encephalopathy (HE) is a neuropsychiatric disorder which arises from acute or chronic liver diseases. Studies in different animal models of HE have described altered locomotor and exploratory activities and learning memory deficits; however, some results are controversial. Therefore, the aim of the present study was to investigate the locomotor and exploratory behavior as well as to access the object recognition memory in a rat model of chronic liver failure, know as bile duct ligated (BDL) rats. Adult female Wistar rats (180±13 g, 60 days-old) were used. All procedures were approved by the University´s Ethics Committee. BDL rats had their common bile duct ligated by two ligatures, the first being made below the junction of the biliary hepatic ducts and the second above the entrance of the pancreatic ducts. The control group consisted in Sham-operated rats. Between the sixth and seventh week after surgery animals were submitted to the following behavioral tasks: open field, elevated plus maze, foot fault and object recognition. Subsequently, blood samples and ascitic fluid were collected and liver and spleen removed for biochemical and pathological analysis, respectively. BDL rats exhibited yellowish color of the fur and tail, an enlarged abdomen and all of them had ascites. Liver and spleen weight was significantly higher in the BDL than in the Sham-operated rats. The plasma analysis showed that the aspartate aminotransferase and alkaline phosphatase activities were significantly higher for the BDL rats as well as the bilirubin amounts. Albumin concentrations were decreased in the BDL rats and it was verified the presence of albumin in the ascitic fluid. For the open field task, BDL rats exhibited a significantly smaller total distance traveled in the arena and a higher duration on immobile episodes than control group. Moreover, total number of stops during the exploratory activity was not different between the BDL and control groups, albeit, the distance traveled between these stops was significantly smaller for the BDL group. There was a significant increase in the time period that the BDL rats stayed in the home-base area when compared to the control group. The number of trips performed during the task was not different between both groups; however, the length of each trip was considerably shorter for the BDL rats. The percentage of time spent in the center of arena was significantly smaller for the BDL than control rats. Regarding elevated plus maze and foot-fault tasks, there was no difference between the BDL and control rats in any parameter analyzed. Concerning the object recognition task, the BDL group did not show difference in the discrimination index for objects A and C in the short-term memory session, whereas the control group exhibited a significantly increased discrimination index for object C when compared to object A. In long-term memory session, both groups had a significantly increased discrimination index for object D when compared to object A. In conclusion, BDL rats exhibited altered spatiotemporal organization of exploratory activity and an impairment of STM in object recognition task. These behavioral alterations were not a consequence of motor deficits or anxiety. The molecular and cellular mechanisms leading to the impairment of the spatiotemporal exploratory activity and memory impairment are still not completely understood and further studies are fundamental to elucidate them. Support: CAPES, CNPq