Inhibition of morphine tolerance by processed Aconiti tuber is mediated by kappa-opioid receptors.
Previously, we found that processed Aconiti tuber (PAT) could inhibit morphine tolerance in mice. In the present study, we investigated mechanisms underlying this effect. Mice received subcutaneous (s.c.) morphine (10 mg/kg) and oral PAT at a subanalgesic dose (0.3 g/kg), once a day for 12 days. Additional PAT-treated groups received morphine and PAT, at 120 min after pretreatment with s.c. clocinnamox mesylate (C-CAM) (0.5 mg/kg), or nor-binaltorphimine (nor-BNI) (5 mg/kg). The antinociceptive effect was assessed with the tail pressure test, at 60 min after the daily s.c. morphine injections were given. In the placebo-treated group, repeated morphine injections caused morphine tolerance, and morphine antinociception was abolished by day 6, whereas in PAT-treated groups, significant antinociception was maintained until day 12, suggesting that PAT inhibited morphine tolerance, thereby sustaining morphine antinociception. C-CAM, a selective mu-opioid receptor (MOR) antagonist, blocked morphine antinociception whereas nor-BNI, a selective kappa-opioid receptor (KOR) antagonist, did not. However, both C-CAM and nor-BNI could block the antinociception maintained by the morphine-PAT combination. Results of the study suggested that chronic treatment with PAT at a subanalgesic dose maintained MOR-mediated morphine antinociception by attenuating development of morphine tolerance, and that this tolerance-attenuating effect of PAT was mediated by KOR.
Shu
Haihua
H
Department of Anesthesiology, Graduate School of Medicine, Surgical Center Research Hospital, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655, Japan.
Arita
Hideko
H
Hayashida
Masakazu
M
Chiba
Shunsuke
S
Sekiyama
Hiroshi
H
Hanaoka
Kazuo
K
D031841:Aconitum; D000701:Analgesics, Opioid / Q000494:pharmacology*; D000818:Animals; D002934:Cinnamates / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004361:Drug Tolerance; D004365:Drugs, Chinese Herbal / Q000494:pharmacology*; D008297:Male; D051379:Mice; D009020:Morphine / Q000494:pharmacology*; D009022:Morphine Derivatives / Q000494:pharmacology; D009270:Naloxone / Q000494:pharmacology; D009271:Naltrexone / Q000031:analogs & derivatives / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology; D010147:Pain Measurement; D017288:Pain Threshold / Q000187:drug effects; D035281:Plant Tubers; D017473:Receptors, Opioid, kappa / Q000187:drug effects* / Q000378:metabolism; D013997:Time Factors
D000701:Analgesics, Opioid; D002934:Cinnamates; D004365:Drugs, Chinese Herbal; D009022:Morphine Derivatives; D009292:Narcotic Antagonists; D017473:Receptors, Opioid, kappa; C076806:clocinnamox; D009270:Naloxone; C051844:norbinaltorphimine; D009271:Naltrexone; D009020:Morphine