Effects Of Orexin A On Morphine-induced Gastrointestinal Dysfunction In Mice

Objective: To investigate the therapeutic effect of orexin A on morphine-induced gastrointestinal dysfunction in mice and its mechanism.Methods: Forty-eight C57B/6 mice were divided into 6 groups(n=8 each),control group(group C),morphine group(group M),morphine + different dose orexin A groups(MOH,MOM,MOL groups)and morphine + mosapride group(group MM).ormal saline 8 ml/kg was subcutaneously injected daily in group C,morphine6mg/kg was subcutaneously injected daily in othe five groups,orexin A 75,50 and25μg/kg were subcutaneously injected daily for 10 days in MOH,MOM,MOL groups,and mosapride 4mg/kg was subcutaneously injected daily in group MM.The feeding intake and fecal water content were calculated and averaged daily.After the last administration,the mice were gavaged black nutritional paste,and the gastric emptying rate and the small intestinal propulsion rate were detected 30 min later.Blood samples were collected from the orbit,and the concentrations of serum acetylcholine(Ach)and gastrin(GAS)were detected by enzyme-linked immunosorbent assay.The mice were then sacrificed,and colon tissues were removed for determination of interstitial cells of Cajal(ICC)-specific marker c-kit and neuro nitric oxide synthase(n NOS)positive cells area(by immunohistochemistry)and expression of c-kit,stem cell factor(SCF),n NOS,vasoactive intestinal peptide(VIP)and substance P(SP)in colon tissues(by Western blot).HE was stained for colon histopathological observation and scoring(HS).Results: Compared with group C,the rate of fecal water content,gastric emptying rate,small intestinal propulsion rate,and serum Ach concentration were significantly decreased,the area of c-kit positive cells was decreased,the area of n NOS positive cells was increased,and the expression of c-kit,SCF and SP was down-regulated,the expression of n NOS and VIP was up-regulated in group M(P <0.05).Compared with group M,the small intestinal propulsion rate and serum GAS concentration were significantly increased,the expression of c-kit and SCF was upregulated,the HS score was decreased in group MOH,and the rate of fecal water content,gastric emptying rate,small intestinal propulsion rate,and serum Ach concentration were significantly increased,the area of c-kit positive cells was increased,the area of n NOS positive cells was decreased,the expression of c-kit,SCF and SP was up-regulated,the expression of n NOS and VIP was down-regulated,the HS score was decreased in group MOM and group MM,and the serum GAS concentration was increased in group MOM,and the serum Ach and GAS concentration were increased,the expression of n NOS and VIP was down-regulated in group MOL(P < 0.05).There was no statistical difference in the above indicators in the remaining groups(P > 0.05).Conclusion: 50μg/kg orexin A can increase the rate of fecal water content,gastric emptying rate,small intestinal propulsion rate of mice,and it can effectively alleviate morphine-induced gastrointestinal dysfunction in mice,the mechanism may be related to promotion GAS secretion,increase the number of goblet cells and ICC in the colon mucosa,regulate excitatory neurotransmitter Ach,SP and inhibitory neurotransmitter NO,VIP release and alleviate intestinal inflammation.Orexin A has a bidirectional regulatory effect on gastrointestinal function in mice.