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

Author(s): Mahnaz Kesmati | Maryem Rezaie | Hadi Fathi-Moghaddam

Journal: Open Access Animal Physiology
ISSN 1179-2779

Volume: 2010;
Issue: default;
Start page: 87;
Date: 2010;
Original page

Mahnaz Kesmati1, Maryem Rezaie1, Hadi Fathi-Moghaddam21Department 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, IranBackground: 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.Keywords: opioid, glucocorticoid, naloxone, mifepristone, hot plate 

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