Effects of naloxone on opioid-induced hyperalgesia and tolerance to remifentanil under sevoflurane anesthesia in rats.

摘要: Background: Opioid antagonists at ultra-low doses have been used with opioid agonists to prevent or limit tolerance. The aim of this study was evaluate whether an dose naloxone combined remifentanil could block opioid-induced hyperalgesia and tolerance under sevoflurane anesthesia in rats. Methods: Male adult Wistar rats were allocated into one four treatment groups (n = 7), receiving (4 µg·kg −1 ·min ) (0.17 ng·kg ), alone, saline. Animals evaluated for mechanical nociceptive thresholds (von Frey) subsequently anesthetized determine the baseline minimum alveolar concentration (MAC). Next, treatments administered, MAC redetermined twice during infusion. experiment performed three times on nonconsecutive days (0, 2, 4). Hyperalgesia considered be a decrease thresholds, whereas reduction by remifentanil. Results: Remifentanil produced significant compared values 2 4 (mean ± SD, 30.7 5.5, 22.1 6.4, 20.7 3.7g 0, 4, respectively) increase (2.5 0.3, 3.0 3.1 0.3 vol% respectively). Both effects blocked coadministration. However, both remifentaniltreated (with without naloxone) developed determined their reduction. Conclusions: An remifentanil-induced but did not change inhalant anesthesia. Moreover, associated also naloxone.