Pain mechanismRegulation of proinflammatory cytokines gene expression by nociceptin/orphanin FQ in the spinal cord and the cultured astrocytes
Section snippets
Animals
Adult male Sprague–Dawley rats (weighing 200–220 g, from Experimental Animal Center, Shanghai Medical College, Fudan University, Shanghai, China) were allowed to acclimate for 1 week and maintained at a room temperature of 22±2 °C and a 12-h light/dark cycle with free access to food and water. The animal protocols were conducted according to the Animals Care and Use Committee of Shanghai Medical College, Fudan University, and conformed to the ethical guidelines of the International Association
Time course of behavioral hypersensitivity
Following a peripheral administration of CFA into the left hind paw, animals showed evident signs of inflammation, which were assessed by localized erythema and an increase in the swelling of the paw, and caused a decrease in hyperalgesia score to noxious thermal stimuli. The hyperalgesia score for thermal stimuli was significantly different from the saline-treated rats. The hyperalgesia score to thermal stimuli decreased markedly at 4 h, and 4, 10 and 14 days in the CFA-treated rats. The
Discussion
We report herein the temporal expression profile of specific proinflammatory cytokines and glial activation in a rodent model of chronic inflammatory pain. Astrocytes in normal CNS are basally active and carry out various functions, including regulation of extracellular ion and neurotransmitter concentrations, availability of neurotransmitter/neuromodulator precursors to nearby neurons and maintenance of extracellular pH. After a lesion, astrocytes undergo extensive hypertrophy of their cell
Conclusion
In summary, the present study showed that astrocyte activation and enhanced cytokine expression in the spinal cord might have a role in eliciting behavioral hypersensitivity. N/OFQ shared a close relationship with cytokines in the CNS. ORL1 receptor was expressed in cultured astrocytes of rat spinal cord. Further it was shown that N/OFQ had a regulatory effect on cytokines mRNA transcripts, which suggested that modulation of nociception by N/OFQ might be dependent on proinflammatory cytokines
Acknowledgment
This project was financially supported by the National Key Basic Research Program (No. 2005CB523306) and the Science Foundation of Shanghai Municipal Commission of Science and Technology (No. 02DZ19150-1).
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