Ultra-low dose (+)-naloxone restores the thermal threshold of morphine tolerant rats.
J Formos Med Assoc
; 112(12): 795-800, 2013 Dec.
Article
em En
| MEDLINE
| ID: mdl-24309169
ABSTRACT
BACKGROUND/PURPOSE:
As known, long-term morphine infusion leads to tolerance. We previously demonstrated that both co-infusion and post-administration of ultra-low dose (±)-naloxone restores the antinociceptive effect of morphine in morphine-tolerant rats. However, whether the mechanism of the action of ultra-low dose (±)-naloxone is through opioid receptors or not. Therefore, in the present study, we further investigated the effect of ultra-low dose (+)-naloxone, it does not bind to opioid receptors, on the antinociceptive effect of morphine.METHODS:
Male Wistar rats were implanted with one or two intrathecal (i.t.) catheters; one catheter was connected to a mini-osmotic pump, used for morphine (15 µg/h), ultra-low dose (+)-naloxone (15 pg/h), morphine plus ultra-low dose (+)-naloxone (15 pg/h) or saline (1 µl/h) infusion for 5 days. On day 5, either ultra-low dose (+)-naloxone (15 pg) or saline (5 µl) was injected via the other catheter immediately after discontinued morphine or saline infusion. Three hours later, morphine (15 µg in 5 µl saline) or saline were given intrathecally. All rats received nociceptive tail-flick test every 30 minutes for 120 minutes after morphine challenge at different temperature (45-52°C, respective).RESULTS:
Our results showed that, both co-infusion and post-treatment of ultra-low dose (+)-naloxone with morphine preserves the antinociceptive effect of morphine. Moreover, in the post administration rats, ultra-low dose (+)-naloxone further enhances the antinociceptive effect of morphine.CONCLUSION:
This study provides an evidence for ultra-low dose (+)-naloxone as a therapeutic adjuvant for patients who need long-term opioid administration for pain management.Palavras-chave
Texto completo:
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Base de dados:
MEDLINE
Assunto principal:
Limiar Sensorial
/
Naloxona
/
Antagonistas de Entorpecentes
Limite:
Animals
Idioma:
En
Revista:
J Formos Med Assoc
Assunto da revista:
MEDICINA
Ano de publicação:
2013
Tipo de documento:
Article
País de afiliação:
Taiwan