ABSTRACT
Objective To evaluate the effects of intrathecal low-dose naloxone,morphine and fentanyl on the expression of motillin (MTL) in the hippocampus of rats with incisional pain.Methods Seventy-two healthy male Sprague-Dawley rats,weighing 180-220 g,aged 6-8 weeks,in which intrathecal catheters were successfully implanted,were randomly divided into 6 groups (n =12 each) using a random number table:normal saline group (NS group),incisional pain group (P group),morphine + fentanyl + incisional pain group (MFP group),and naloxone (0.2,1.0 and 5.0 ng/kg) + morphine + fentanyl groups (MFPN1,MFPN2 and MFPN3 groups).Incisional pain was induced by an incision made into the plantar surface of the right hindpaw.At 20 min before induction of incisional pain,the mixture of morphine 5 μg/kg and fentanyl 0.25 mg/kg was injected intrathecally in group MFP,and the mixture of naloxone 0.2,1.0 and 5.0 ng/kg,morphine and fentanyl were injected intrathecally in MFPN1,MFPN2 and MF-PN3 groups,respectively.Six rats in each group were selected,and the mechanical paw withdrawal threshold (MWT) and thermal paw withdrawal latency (TWL) were measured at 24 h before intrathecal catheterization (T0,baseline),at 24 h before induction of incisional pain (T1),and at 1,3 and 6 h after operation (T2-4).The left 6 rats in each group were selected and sacrificed at 6 h after operation,and the hippocampi,body of the stomach and duodenum were removed for detection of MTL content by enzyme-linked immunosorbent assay.Results Compared with group NS,the MWT was significantly decreased,and the TWL was shortened at T2-4 in P and MFPN3 groups,the MWT was significantly decreased,and the TWL was shortened at T4 in group MFPN1,and the TWL was prolonged at T2 in group MFPN2,the MTL contents in hippocampus and body of the stomach were significantly decreased in P,MFP,MFPN1 and MF-PN3 groups,the MTL contents in duodenum were increased in P and MFPN3 groups,and the MTL contents in duodenum were decreased in MFP and MFPN1 groups (P＜0.05),and no significant change was found in the parameters mentioned above in group MFPN2 (P＞0.05).Conclusion Intrathecal naloxone 1.0 ng/kg combined with morphine and fentanyl can inhibit up-regulation of the expression of MTL in the hippocampus of rats with incisional pain,and then is involved in the maintenance of stable gastrointestinal motility.