The κ-opioid agonist (±)-bremazocine elicits peripheral antinociception by activation of the l-arginine/nitric oxide/cyclic GMP pathway

• Published in: European journal of pharmacology 2002-11, Vol.454 (1), p.19-23
• Main Authors: Amarante, Luiz H, Duarte, Igor Dimitri Gama
• Format: Article
• Language: English
• Subjects: Analgesics - pharmacology; Animals; Arginine - metabolism; Benzomorphans - pharmacology; Bremazocine; Carrageenan; Cyclic GMP; Cyclic GMP - metabolism; Guanylate Cyclase - antagonists & inhibitors; Hyperalgesia - drug therapy; Hyperalgesia - metabolism; Male; Methylene Blue - pharmacology; Nitric oxide; Nitric Oxide - metabolism; Nitric Oxide Synthase - antagonists & inhibitors; Nitroarginine - pharmacology; Pain - drug therapy; Pain - metabolism; Peripheral antinociception; Phosphodiesterase Inhibitors - pharmacology; Purinones - pharmacology; Rats; Rats, Wistar; Receptors, Opioid, kappa - antagonists & inhibitors; κ-Opioid receptor
• ISSN: 0014-2999; 1879-0712
• DOI: 10.1016/S0014-2999(02)02275-6

In view of the scarce information about the analgesic mechanism of κ-opioid receptor agonists, the objective of the present study was to determine whether nitric oxide (NO) is involved in the peripheral antinociception of bremazocine, a κ-opioid receptor agonist. Three drugs all interfering with the l-arginine/NO/cyclic GMP pathway were tested using the rat paw model of carrageenan-induced (250 μg) hyperalgesia: (a) N G-nitro- l-arginine (a nonselective NO-synthase inhibitor), (b) methylene blue (a guanylate cyclase inhibitor), and (c) zaprinast (a cyclic GMP phosphodiesterase inhibitor). Intraplantar administration of bremazocine (20, 40 and 50 μg) caused a dose-dependent peripheral antihyperalgesia against carrageenan-induced hyperalgesia. The possibility of the higher dose of bremazocine (50 μg) having central or systemic effect was excluded since administration of the drug into the left paw did not elicit antinociception in the contralateral paw. However, when the dose of bremazocine was increased to 100 μg, a significant increase in the nociceptive threshold was observed, as measured in the hyperalgesic contralateral paw. Peripheral antihyperalgesia induced by bremazocine (50 μg) was significantly reduced in a dose-dependent manner when N G-nitro- l-arginine (6, 9, 12 and 25 μg) or methylene blue (250, 375 and 500 μg) was injected before. Previous treatment with 50 μg of zaprinast (which had no effect when administered alone) potentiated the antihyperalgesic effect of bremazocine (20 μg). Our data suggest that bremazocine elicits peripheral antinociception by activation of the l-arginine/NO/cyclic GMP pathway and that nitric oxide is an intermediary in this mechanism, forming cyclic GMP.