ABSTRACT
Objective:To evaluate the effect of orexin A on morphine-induced gastrointestinal dysfunction in mice.Methods:Forty SPF C57B/6 mice, aged 6-8 weeks, half male and half female, weighing 18-22 g, were divided into 5 groups ( n=8 each) using a random number table method: control group (group C), morphine group (group M) and morphine + different doses of orexin A groups (MOH, MOM and MOL groups). Normal saline 8 ml/kg was subcutaneously injected daily in group C, morphine 6 mg/kg was subcutaneously injected daily in the other four groups, and orexin A 75, 50 and 25 μg/kg were subcutaneously injected daily for 10 days at the same time in MOH, MOM and MOL groups.The fetal water content was calculated and averaged daily.After the last administration, the mice were gavaged with black nutrient paste, and the gastric emptying rate and small intestinal propulsion rate were detected 30 min later.Blood samples were collected from the orbit, and the concentration of serum gastrin (GAS) was detected by enzyme-linked immunosorbent assay.The mice were then sacrificed, and colon tissues were removed for determination of c-kit positive cell area (by immunohistochemistry) and expression of c-kit, substance P (SP) and neural nitric oxide synthase (nNOS) in colon tissues (by Western blot). Results:Compared with group C, the rate of fecal water content, gastric emptying rate, small intestinal propulsion rate and serum GAS concentration were significantly decreased, the area of c-kit positive cells was decreased, and the expression of c-kit and SP was down-regulated, and the expression of nNOS was up-regulated in group M ( P<0.05). Compared with group M, the small intestinal propulsive rate and serum GAS concentration were significantly increased, and the area of c-kit positive cells was increased, and the expression of c-kit was up-regulated in group MOH, the rate of fecal water content, gastric emptying rate, small intestinal propulsion rate and serum GAS concentration were significantly increased, the area of c-kit positive cells was increased, and the expression of c-kit and SP was up-regulated, and the expression of nNOS was down-regulated in group MOM, and the serum GAS concentration and c-kit positive cell area were significantly increased in group MOL ( P<0.05). Conclusions:Orexin A 50 μg/kg can effectively alleviate the gastrointestinal dysfunction induced by morphine in mice, and the mechanism may be related to promotion of GAS secretion, interstitial cells of Cajal growth and SP release and inhibition of NO release.