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  • Articles: DFG German National Licenses  (3)
  • Morphine  (3)
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  • Articles: DFG German National Licenses  (3)
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  • 1
    Electronic Resource
    Electronic Resource
    In vivo apparent affinity and efficacy estimates for μ opiates in a rat tail-withdrawal assay (1998)
    Springer
    Psychopharmacology 136 (1998), S. 15-23 
    Details
    ISSN: 1432-2072
    Keywords: Key words Etonitazene ; Morphine ; Buprenorphine ; Etorphine ; GPA 1657 ; Affinity ; Efficacy ; Antinociception ; Clocinnamox
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Experiments in a rat tail-withdrawal assay tested the hypothesis that the magnitude and pattern of antagonism of μ opiate agonists by the insurmountable μ opioid antagonist clocinnamox are inversely related to agonist efficacy. In addition, these experiments examined whether this antagonism could be quantified to yield apparent affinity and efficacy estimates for the pharmacological characterization of five opiate agonists. Etonitazene, etorphine, morphine, buprenorphine, and GPA 1657 produced dose-dependent increases in tail-withdrawal latency until 100% maximum possible effect (%MPE) was obtained. Morphine required a higher dose of clocinnamox for a 50% reduction in maximal antinociceptive effect than did buprenorphine or GPA 1657. In contrast, no dose of clocinnamox tested decreased the%MPE for etonitazene or etorphine. These data suggest a rank order of relative efficacy of etonitazene ≥ etorphine 〉 morphine ≥ GPA 1657 ≥ buprenorphine. Similarly, numerical analysis of these data yielded the following apparent affinity and efficacy estimates: etonitazene (0.38 mg/kg, 128); etorphine (0.68 mg/kg, 125); morphine (50 mg/kg, 38), GPA 1657 (6.6, 39); and buprenorphine (0.042 mg/kg, 2.2). These data illustrate that in vivo affinity and efficacy estimates for a number of agonists are remarkably similar across different methods of analysis and are useful for drug classification.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002130050534
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    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Tolerance and cross-tolerance to morphine-like stimulus effects of µ opioids in rats (1997)
    Springer
    Psychopharmacology 133 (1997), S. 17-28 
    Details
    ISSN: 1432-2072
    Keywords: Key words Tolerance ; Drug discrimination ; Fentanyl ; Morphine ; Nalbuphine ; Efficacy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The purpose of these experiments was to examine the relationship of agonist relative efficacy to the pattern of tolerance and cross-tolerance to the morphine-like stimulus effects of three opioid agonists. Rats were trained to discriminate 3.2 mg/kg morphine from saline under fixed-ratio 15 schedule of food reinforcement. Morphine, nalbuphine, and fentanyl produced dose-dependent increases in morphine-like stimulus effects and decreases in response rates. Repeated treatment with 20 mg/kg per day morphine increased the ED50 for stimulus control by fentanyl, morphine, or nalbuphine two-, four-, or 40-fold, respectively. Repeated treatment with 64 mg/kg per day nalbuphine increased the ED50 for stimulus control for morphine by two-fold, but lower or higher treatment doses had no significant effect. Treatment with 100 mg/kg per day nalbuphine increased the ED50 for nalbuphine by six-fold. Repeated treatment with 0.22 mg/kg per day fentanyl increased the ED50 for stimulus control by fentanyl or morphine by approximately two-fold. Comparisons among treatment conditions suggested that magnitude of tolerance to morphine-like stimulus effects did not vary as an inverse function of the relative efficacy of the agonist used for repeated treatment. Rather repeated morphine and fentanyl treatments produced comparable tolerance, whereas repeated nalbuphine treatment did not evoke substantial tolerance. Comparisons within treatment conditions, however, suggested that magnitude of tolerance may vary inversely with relative efficacy of the agonist tested for morphine-like stimulus effects. During treatment with morphine or fentanyl, greater tolerance was observed to the morphine-like stimulus effects of the lower efficacy agonist relative to the higher efficacy agonist.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002130050366
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    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    In vivo apparent pA2 analysis in rats treated with either clocinnamox or morphine (1996)
    Springer
    Psychopharmacology 125 (1996), S. 113-119 
    Details
    ISSN: 1432-2072
    Keywords: Naltrexone ; Nalbuphine ; Clocinnamox ; Morphine ; Tolerance ; Drug discrimination ; pA2 analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Experiments tested the hypothesis that loss of agonist potency or effectiveness following irreversible antagonist or chronic agonist treatment may result from affinity changes at μ opioid receptors. Apparent affinity of naltrexone or nalbuphine for μ opioid receptors was measured in vivo in rats treated with either a single dose of the irreversible antagonist clocinnamox or repeated doses of morphine. Apparent affinity of each antagonist was estimated from its potency as an antagonist of discriminative stimulus or rate-decreasing effects of morphine in rats trained to discriminate 3.2 mg/kg morphine and saline. In control rats, apparent pA2 values for naltrexone and nalbuphine were 7.5–7.6 and 5.3, respectively. In clocinnamox-treated rats, apparent pA2 values for naltrexone were 7.2–7.7, suggesting that clocinnamox treatment did not alter affinity of naltrexone for sites through which morphine exerts behavioral effects. In rats treated repeatedly with morphine, apparent pA2 values for nalbuphine were 5.1–5.3, suggesting that repeated morphine treatment did not alter affinity of nalbuphine for these sites. The observation that neither clocinnamox nor repeated morphine treatment altered in vivo affinity estimates for naltrexone or nalbuphine, respectively, suggests that the reductions in agonist potency produced by these treatments do not result from changes in affinity at μ opioid receptors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02249409
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    Paper (German National Licenses)
    Fulltext
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