Does CA1 dopaminergic system play a role in cholestasis induced hypothermia?

Possible involvement of the opioidergic system in the modulation of body temperature, jumping behavior and memory process in cholestatic and addicted mice

Cholestasis is related to an increased plasma level of endogenous opioid levels. Naloxone-induced withdrawal syndrome has been reported in a mouse model of cholestasis. Moreover, studies revealed that the memory process is affected by cholestasis. Thus, we aimed at determining whether pharmacological manipulation of the opioidergic system is involved in signs of cholestasis disease such as hypothermia and withdrawal behaviors such as jumping behavior as well as memory process in mice. Cholestasis was induced by bile duct resection in mice and physical dependence was induced by administration of morphine and/or tramadol three times daily (8, 12 and 16 h) at the doses of 25, 50 and 75 mg/kg during three consecutive days. The memory process was assessed by a step-down passive avoidance test. Our results indicated that cholestatic mice showed hypothermia whereas cholestatic- and drug dependent mice indicated hyperthermia. Moreover, administration of morphine (50 mg/kg) and/or tramadol (50 mg/kg) on the 4th day, 2 h before naloxone injection significantly decreased latency to first jumping but increased the number of jumping and rearing behavior as well as locomotor activity in BDL-vs. sham-operated mice. In addition, the latency time of the step-down test decreased in BDL-vs. sham-operated group, showing impairment of memory in BDL mice. The results of this study support the evidence that (1) the opioidergic system involved in thermoregulation of cholestasis mice, (2) μ-opioid receptors play an important role in withdrawal behaviors, and (3) memory process is affected by cholestasis and addiction in mice.

Erythropoietin ameliorates the motor and cognitive function impairments in a rat model of hepatic cirrhosis

Hepatic encephalopathy (HE) is a serious consequence of hepatic cirrhosis (HC). Previous studies have demonstrated cognitive impairments in both clinical and animal experiments of HC. Some potential therapeutic agents have been used to alleviate the cognitive symptoms in the animal models of HC. In the current study, the possible effect of erythropoietin (ERY) as a potent neuroprotective agent on motor and cognitive impairments induced by HC has been studied. Male Wistar rats (180-200 g) underwent bile duct ligation (BDL) or sham surgery. Administration of ERY (5,000 IU/kg, i.p., daily for three days) was initiated 2 weeks after surgery and lasted for the next 28 days. Open field, rotarod, Morris water maze and passive avoidance learning was used to evaluate the motor and cognitive function of the animals. ANOVA and repeated measures ANOVA were used to analyze the data. p < 0.05 was considered statistically significant. BDL rats had an increased level of hepatic enzymes and bilirubin. Impairment of balance function by BDL was reversed by ERY. Spatial and passive avoidance learning impairments observed in BDL rats were also reversed by chronic administration of ERY. ERY can be offered as a potential neuroprotective agent in the treatment of patients with HC that manifest mental dysfunctions. Though further studies are needed to clarify the exact mechanisms, the neuroprotective properties of ERY against BDL impairments were demonstrated in the current study.