10-13-2002, 12:08 PM
• Lin CR, Chuang YC, Cheng JT, Wang CJ and Yang LC (2002). Intrathecal clonidine decreases spinal nitric oxide release in a rat model of complete Freund's adjuvant induced inflammatory pain. Inflammation. 26 (4): 161-6. Summary: A long-lasting antihyperalgesic effect has been demonstrated for intrathecal (IT) clonidine, an alpha2-adrenergic agonist. In the present study, the mechanism and antihyperalgesic effects of IT clonidine were examined post-treatment in a rat model of Complete Freund's Adjuvant (CFA)-induced inflammatory hyperalgesia. Using a chronic model of spinal cord dialysis, we examined the effect of the adjuvant-induced inflammation on spinal release of nitric oxide (NO) and the development of chronic pain and assessed the antinociceptive effects and mechanisms of the alpha2-adrenergic agonist, clonidine (IT). Chronic, persistent inflammatory pain was induced by left hind paw injection of 0.3 ml CFA prepared in a mixture with Mycobacterium butyricum. Rats were randomly assigned to groups receiving IT clonidine in discrete doses of 1, 10 or 50 microg, 3 or 24 hr post-inflammation. Measurement of total NOx (NO + NO2- + NO3-) was used to determine NO release into the cerebrospinal fluid. Rat thermal antinociception was assessed using a radiant heat thermal hyperalgesia model. CFA injection resulted in significant thermal hyperalgesia throughout the four days of observation. A dose-dependent suppression of thermal hyperalgesia and spinal NO release was observed after IT clonidine treatment. Evidence from this CFA-induced inflammatory pain model suggests that clonidine's spinal antihyperalgesic mechanisms act through inhibition of spinal NO release. <http://www.ncbi.nlm.nih.gov/htbin-post/Entrez/query?db=m&form=6&dopt=r&uid=12184629> Anesthesiology Research Laboratory, Kaohsiung Chang Gung Memorial Hospital, Chang Gung University, Kaohsiung Hsien, Taiwan.