Pharmacological properties of R-84760, a novel kappa-opioid receptor agonist.
The pharmacological properties of a structurally novel kappa-opioid receptor agonist, (3R)-3-(1-pyrrolidinylmethyl)-4-[(1S)-5,6-dichloro-1-indancarbo nyl]- tetrahydro-1,4-thiazine hydrochloride (R-84760), were examined. In an opioid receptor binding assay with a guinea pig brain membrane fraction, R-84760 showed a 5 times higher affinity for the kappa-opioid receptor than CI-977, the most potent reference kappa-opioid receptor agonist, and selectivity of R-84760 for the kappa-opioid receptor was higher than that of U-69593, a highly selective kappa-opioid receptor agonist. R-84760 was functionally 2.5 times more potent than CI-977 as a kappa-opioid receptor agonist in rabbit vas deferens. Subcutaneously administered R-84760 had an antinociceptive effect in the phenylquinone writhing test in mice and its potency was 5-846 times higher than those of CI-977, U-50488, morphine, pentazocine and butorphanol. On oral administration, R-84760 was 20-2077 times more potent than the same reference drugs. The antinociceptive effect of R-84760 was not antagonized by naloxone in a dose at which naloxone antagonized the effect of morphine, but on the other hand nor-binaltorphimine antagonized the effect of R-84760 at a dose which did not affect the effect of morphine. R-84760 and the reference kappa-opioid receptor agonists produced sedative and diuretic effects in mice with the same order of potency as for the antinociceptive effect. Tolerance to the antinociceptive effect of R-84760 barely developed, and naloxone-induced jumping tests for morphine-like physical dependence of R-84760 gave negative results.[1]References
- Pharmacological properties of R-84760, a novel kappa-opioid receptor agonist. Fujibayashi, K., Sakamoto, K., Watanabe, M., Iizuka, Y. Eur. J. Pharmacol. (1994) [Pubmed]
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