| The Effect of Intrathecal Morphine, Clonidine and MK801 on the Formalin Test in the Rats. |
|
Jae Youn Kwon, Chul Hong Kim, Hae Kyu Kim, Seong Wan Baik, Inn Se Kim, Kyoo Sub Chung |
1Department of Anesthesiology, Pusan National University Hospital, Pusan, Korea.
2Department of Anesthesiology, Seoul National University College of Medicine, Seoul, Korea. |
|
|
|
|
|
| Abstract |
BACKGROUND
There has been much interest in the involvement of wind-up in the hyperalgesia and allodynia of chronic pain syndrome. To investigate the behavioral parallels of this wind-up phenomenon, we evaluated the effects of intrathecal morphine, clonidine and MK801 on the formalin test in the rats.
METHOD
All experimental animals were divided randomly into six groups. In group 1(n=7), normal saline 50 l was administered through the intrathecal catheter(PE10, 8 cm in length). In group 2(n=7), morphine 10 g was administered through the catheter. In group 3(n=7), group 4(n=7), group 5(n=7) and group 6(n=7), clonidine 10 g, clonidine 20 g, MK801 1 g, MK801 10 g was administered in same manner, respectively. Thirty min after recoverying from anesthesia, 50 l 5% formalin was injected in the hind paw. To quantify the formalin response, we counted the number of spontaneous flinching for 60 min.
RESULT
Intrathecal morphine(group 2) decreased the number of paw flinches in both phases 1 and 2 readily compared to control(p<0.05). In the clonidine(group 3 and 4), both groups decreased the number of flinching in both phases 1 and 2, but there was no significant difference between two groups. In group 5, intrathecal MK-801 decreased the number of paw flinches in phase 2. In group 6, intrathecal MK-801 decreased the number of paw flinches in both phases 1 and 2.
CONCLUSION
This study suggest that wind-up is readily blocked by pretreatment of morphine, clonidine and MK801. |
| Key Words:
Analgesics; clonidine; MK801; morphine; Anesthetic technique; intrathecal; Animals; rats; Pain; formalin test |
|
PDF Links
Full text via DOI
Download Citation
