Effects of epidural infusion of morphine combined with small-dose naloxone on gastrointestinal interstitial cells of Cajal in rabbits.

OBJECTIVE: To study the effect of epidural infusion of morphine combined with small-dose naloxone on gastrointestinal interstitial cells of Cajal (ICC) in rabbits. MATERIALS AND METHODS: A total of 80 healthy New Zealand rabbits were selected as objects of study, and divided into normal saline control group (Group NS, n=20), morphine group (Group M, n=20), naloxone group (Group N, n=20), and morphine + naloxone group (Group NM, n=20). Rabbits in four the groups received epidural catheterization for continuous drug infusion for 7 d, and epidural analgesia pump was connected. Visual analogue scale (VAS) score, intestinal propulsion rate, c-kit expression, and ICC count were detected and compared among four groups of rabbits. RESULTS: No statistical differences of occurrence rates regarding constipation as well as expressions of c-kit and ICC count in the proximal colon were shown among rabbits in Group NS, Group N, and Group NM during drug administration (p>0.05). However, the occurrence rates of constipation of rabbits in Group M at 3-7 d were statistically higher than those in Group NS, Group N, and Group NM, and the differences were statistically significant (p<0.05). Moreover, the VAS scores in Group NS and Group N were significantly higher than those in Group M and Group NM, while the scores in Group M were also significantly increased compared to that in Group NM (p<0.05). The intestinal propulsion rates, expressions of c-kit and ICC counts of rabbits in Group NS, Group N, and Group NM were statistically higher than that in Group M (p<0.05). CONCLUSIONS: Epidural infusions of morphine combined with small-dose naloxone effectively inhibit the gastrointestinal motility of rabbits via the reduction of ICC in the proximal colon of the gastrointestinal tract of rabbits. Moreover, small-dose of naloxone enhances the analgesic effect, and reduces the risk of adverse reactions.