| Objective: To study the effects of two methods of sufentanil analgesia on dynorphin and prostaglandin E2 in rabbits blood by setting up the formalin pathological pain model.Methods: Eighteen healthy rabbits were randomly divided into three groups, (n=6 in each),namely intravenous analgesia group (group A), epidural analgesia group (group B)and control group (group C) . 5% formalin solution 0.5ml was injected into the hind paw of rabbits in each group to set up formalin pain model. Rabbits in the group A and B were respectively administered with sufentanil 0.46μg·kg-1 intravenously and 0.64μg·kg-1 epidurally, rabbits in the group C were injected with saline 0.5 mL intravenously. The spontaneous nociceptive behavior was quantified and recorded for a period of 45 minutes ,and two phase cumulative pain grade(the first phase is from 0 to 10 minutes,and the second phase is from 10 to 45 minutes). Serial blood samples were taken before the experiment (T0),10 min after analgesia (T1) ,20 min after analgesia (T2),40 min after analgesia (T3),2 h after analgesia (T4),8 h after analgesia (T5),24 h after analgesia (T6) and 48 h after analgesia (T7) to determine the levels of dynorphin and prostaglandin E2 by ELESA.Results: Sufentanil analgesia can reduce the pain of rabbits effectively, the pain score of group A and group B decreased steadily , and the pain of rabbits in group C last longer than that of group A and group B. The pain responses in both phase were inhibited significantly in GroupA and GroupB compared with GroupC(P<0.05). There was no significant difference in the pain responses of GroupA and GroupB during the two phase(P>0.05). There were no significant difference in dynorphin and prostaglandin E2 among three groups before experiment. Compared with T0, the level of dynorphin in group C showed a significant ascent at T1,T2,T3,T4,T5,T6 and T(7P<0.05),the level of dynorphin in group B kept steady from T0 to T3,and rose at T4, And the level of dynorphins in group B kept steady from T0 to T4,and rose at T5. The level of prostaglandin E2 in group C is much higher than group A and B at T1,T2,T3,T4,T5,T6 and T7(P<0.05). The levels of prostaglandin E2 in group A and B dropped to the level of T0 at the T6 and T5 respectively, but in the control group it still remained at a high level at T7.Conclusion: Two methods of analgesia are effective, sufentanil analgesia could help to stabilize the level of dynorphins and restrain the level of prostaglandin E2,and the effect of epidural method is better than that of intravenous method.
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