Effect of tramadol on immune responses and nociceptive thresholds in a rat model of incisional pain |
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| Authors: | Liu Yong-Min Zhu Sheng-Mei Wang Kui-Rong Feng Zhi-Ying Chen Qing-Lian |
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| Institution: | Department of Anesthesiology, the First Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou 310003, China |
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| Abstract: | Objective To evaluate the effects of tramadol on the proinflammatory responses in a rat model of incisional pain by investigating its
effects on nociceptive thresholds and serum interleukin-6 (IL-6) and IL-2 levels.
Methods Forty-two male Sprague-Dawley (SD) rats scheduled for plantar incision were randomly divided into 7 groups (n=6 in each group). Rats in Group 1 receiving general anesthesia with no incision were served as control; At 30 min before
skin incision, Groups 2∼5 were given 5 ml normal saline or 1, 10, and 20 mg/kg tramadol, respectively, intraperitoneally (i.p.);
Group 6 received 10 mg/kg tramadol after operation; Group 7 received 10 mg/kg tramadol before incision, followed by 200 μg/kg
naloxone after operation. Mechanical allodynia was measured by electronic von Frey filament to evaluate the nociceptive thresholds
1 h before incision, and 1 h and 2 h after operation. Serum IL-6 and IL-2 levels were measured by enzyme-linked immunosorbent
assay (ELISA) 2 h after operation.
Results Mechanical thresholds decreased significantly and serum IL-6 level increased significantly after operation in Group 2 compared
with control (P<0.01), and these changes were reversed respectively by tramadol in a dose-dependent manner (P<0.05 and P<0.01, respectively). IL-2 level remained unchanged after operation in Group 2, but decreased in Group 3 (P<0.05), then gradually returned to the normal level in Groups 4 and 5. The intraperitoneally injected tramadol (10 and 20
mg/kg) produced a potent and dose-dependent antinocicptive effect on the lesioned paw. The antinocicptive effects of tramadol
were partially antagonized by naloxone (200 μg/kg), suggesting an additional non-opioid mechanism.
Conclusion The results suggest that tramadol could be a good choice for the treatment of pain under the conditions that immunosuppression
may be particularly contraindicated.
Project (No.2006A031) supported by the Medical Foundation Insurance of Zhejiang Health Bureau, China |
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| Keywords: | Tramadol Pain Mechanical allodynia lnterleukin-6 (IL-6) Interleukin-2 (IL-2) Rat |
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