[Comparison of the antagonistic effects of 6 beta-naltrexol and naltrexone against morphine analgesia].
OBJECTIVE
To compare the antagonistic effects of 6 beta-naltrexol and naltrexone against morphine analgesia.


METHODS
The effects of 6 beta-naltrexol and naltrexone against morphine analgesia were observed in mouse heat radiant tail-flick assay and in mouse (55 +/- 1) degrees C hot plate test. The displacement of 6 beta-naltrexol and naltrexone on binding to CHO-mu receptor was observed by radioligand binding study.


RESULTS
6 beta-naltrexol antagonized morphine analgesia but the potency was (6.1 +/- 1.7)% that of naltrexone. The effective duration of 6 beta-naltrexol was 3-4 times that of naltrexone and the peak time of the response was about 0.5-1 h after s.c. equivalent efficacy dose (ED95) in two models. Like naltrexone, 6 beta-naltrexol was effective by oral administration and the potency ratio of p.o./s.c. was 1/3. As an antagonist to opioid receptor, the displacement of 6 beta-naltrexol was about 12.5% that of naltrexone, which was almost in agreement with the efficacies against morphine analgesia in mouse.


CONCLUSIONS
Compared with naltrexone, 6 beta-naltrexol was less potent but duration was longer.
Yan
Ling-di
LD
Institute of Pharmacology and Toxicology, Academy of Military Medical Sciences, Beijing 100850, China. YanLD-1999@163.com
Gong
Ze-hui
ZH
Yao
Xia-jun
XJ
Qin
Bo-yi
BY
D000698:Analgesia; D000701:Analgesics, Opioid / Q000037:antagonists & inhibitors*; D000818:Animals; D005260:Female; D008297:Male; D051379:Mice; D009020:Morphine / Q000037:antagonists & inhibitors*; D009271:Naltrexone / Q000031:analogs & derivatives* / Q000494:pharmacology*; D009292:Narcotic Antagonists / Q000494:pharmacology*; D017288:Pain Threshold / Q000187:drug effects; D017450:Receptors, Opioid, mu / Q000378:metabolism
D000701:Analgesics, Opioid; D009292:Narcotic Antagonists; D017450:Receptors, Opioid, mu; C010410:6 beta-hydroxynaltrexone; D009271:Naltrexone; D009020:Morphine