Effects of Cholestasis on Passive Avoidance Memory in Bile Duct Ligated Male Rats: Role of Opioidergic Systems

Memory is impaired in patients with liver disease. Opioidergic systems are known to be involved in cholestasis. The aim of this study was toinvestigate the possible effect of this system in BDLinduced memory formation in the male rat. This study investigated the impact of cholestasis progression on the acquisition and retention times in the passive avoidance test. Materials and Methods: Cholestasis was inducedin male Wistar rats by ligating the main bile duct. Male rats divided into none operated controls, sham-operated, and BDL groups. Memory was assessed by the passive avoidance learning test at day 7, day 14, and day 21 post-bile duct ligation. The serum levels of bilirubin,alanine aminotransferase, and alkaline phosphatase were measured. Results: The results showed initial latency was not affected till 21 post-bile duct ligation whereas decreases memory retrieval 7, 14 and 21 days post BDL. Therefore, short-term memory was affected in the early stage of cholestasis. Intraperitoneal injection of naloxone (0.6 and 0.8 mg/kg) ), 30 min before testing, 7 days after bile duct ligation did not show a significantly altered in memory acquisition, whereas injection of morphine (4 mg/kg and 6 mg/kg) 30 min before testing 7 days after bile duct ligation, showed a significantly increased in acquisition time. Both doses of morphine could restore cholestasis - induced amnesia in stepthrough passive avoidance test. Also, injection of a dose of naloxone (0.6 mg/kg) 15 min before the injection of a dose of morphine (6 mg/kg) exerted no effect on memory acquisition in the 7 days post-BDL rat. Conclusion: The result show impaired of memory happens in the early