The effect of remifentanil-induced hyperalgesia by different dose of μ-receptor antagonist CTOP

Abstract

Objective To investigate the effect of different dose of μ-receptor antagonist CTOP on remifentanil-induced hyperalgesia in incisional pain rat model by observing rats' paw withdrawal thermal latency (PWTL)and the dynorphin expression in spinal cord.Methods Thirty male SD rats were randomly divided into 5 groups (n=6):control group (A),incisional pain group (B),incisional pain +remifentanil group (C),incisional pain + remifentanil +CTOP lower dose group (D),incisional pain + remifentanil+CTOP higher dose (E).All rats were anesthetized with intraperitoneal 5％ chloral hydrate (350 mg/kg).Ten min after administered intravenously with 0.4 ml saline in group A,group B and group C,with 0.5 μg/kg CTOP in group D and 0.5 mg/kg CTOP,rats in all groups except group A were underwent right hind paw surgery.Meanwhile,rats in group A and group B were infused intravenously with saline,and rats in group C,group D and group E were infused intravenously with remifentanil of 40 μg/kg by lasting 30 min.24 h (T2) later,24 h later,all rats were sacrificed and spinal cord tissues were separated for detecting the expression of dynorphin by ELISA.PWTL was tested at time before anaesthesia (T0),2 h (T2) and 24 h (T2) after paw surgery.Results PWTL were significantly lower in group C [(10.2±3.0) s at T1 and (6.2±2.6) s at T2] than that in group A [(13.3±2.4) s at T1 and (13.4±2.2) s at T2] and group B [(13.5±2.7) s at T1 and (11.5±4.1) s at T2] compared with group A.Dynorphin expression in group C(172±17) ng/Lwere higher than that in group A (78±9) ng/L and group B(120±10) ng/L(P＜0.05).Compared with group C,PWTL were higher and dynorphin were lower significantly in group D and E (P＜0.05).There were different in the dynorphin expression between group D and group E.Conclusions In rat model of incisional pain,remifentanil could enhance postoperative pain,μ-receptor antagonist(CTOP)could reduce the hyperalgesia induced by remifentaniland the lower dose is more effective. Key words: Remifentanil; Hyperalgesia; Incision pain; CTOP; Dynorphin