Interaction between glucocorticoids and opioids in nociception in young and adult rats

teraction between glucocorticoids and opioids in nociception in young and adult rats Original Research (2925) Total Article Views Authors: Mahnaz Kesmati, Maryem Rezaie, Hadi Fathi-Moghaddam Published Date November 2010 Volume 2010:2 Pages 87 - 92 DOI: http://dx.doi.org/10.2147/OAAP.S10007 Mahnaz Kesmati1, Maryem Rezaie1, Hadi Fathi-Moghaddam2 1Department of Biology, Faculty of Sciences, Shahid Chamran University, Ahvaz; 2Department of Physiology and Persian Gulf Physiology Research Center, School of Medicine, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran Background: The aim of this study was to examine the relationship between the glucocorticoid and opioid systems in the modulation of nociception in young and adult rats. Materials and methods: The experiments were done in young and adult Wistar rats, using morphine 5 mg/kg, and naloxone 2 mg/kg as a μ-opioid receptor agonist. Dexamethasone 1 mg/kg and mifepristone (RU486) 20 mg/kg were used as a glucocorticoid receptor agonist and antagonist, respectively. Hind paw licking latency was measured by hot plate after intraperitoneal administration of drugs. Results: The results showed that morphine and dexamethasone had significant analgesic effects (P < 0.001, P < 0.01, respectively) in both age groups. Coadministration of morphine and dexamethasone did not induce a greater analgesic effect in comparison with morphine alone in either age group. Mifepristone prevented the analgesic effect of morphine in the adult animals (P < 0.001), but had no effect in young animals. The analgesic effect of dexamethasone was inhibited by naloxone in both groups (P < 0.01). Conclusion: These results suggest that glucocorticoids regulate opioid-induced analgesia from the age of puberty, but opioids regulate glucocorticoid-induced analgesia in prepubescent animals. Thus, there is a clear overlapping effect between the two pain modulation systems.