Comparison of the antagonistic effects of 6 beta-naltrexol and naltrexone against morphine analgesia
Yan, L-di.; Gong, Z-hui.; Yao, X-jun.; Qin, B-yi.
Yao Xue Xue Bao 38(8): 578-581
2003
ISSN/ISBN: 0513-4870 PMID: 14628446 Document Number: 560783
Aim: To compare the antagonistic effects of 6beta-naltrexol and naltrexone against morphine analgesia. Methods: The effects of 6beta-naltrexol and naltrexone against morphine analgesia were observed in mouse heat radiant tail-flick assay and in mouse (55+-1) degreeC hot plate test. The displacement of 6beta-naltrexol and naltrexone on binding to CHO-mu receptor was observed by radioligand binding study. Results: 6beta-naltrexol antagonized morphine analgesia but the potency was (6.1+-1.7) % that of naltrexone. The effective duration of 6beta-naltrexol was 3-4 times that of naltrexone and the peak time of the response was about 0.5-1 h after sc equivalent efficacy dose (ED95) in two models. Like naltrexone, 6beta-naltrexol was effective by oral administration and the potency ratio of po/sc was 1/3. As an antagonist to opioid receptor, the displacement of 6beta-naltrexol was about 12.5% that of naltrexone, which was almost in agreement with the efficacies against morphine analgesia in mouse. Conclusion: Compared with naltrexone, 6beta-naltrexol was less potent but duration was longer.