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  • 1
    Electronic Resource
    Electronic Resource
    Pharmacological profile of a potent, efficacious fentanyl derivative in rhesus monkeys (1992)
    Springer
    Psychopharmacology 109 (1992), S. 291-298 
    Details
    ISSN: 1432-2072
    Keywords: Opioid ; Drug discrimination ; Analgesia ; Fentanyl ; Rhesus monkey ; Competitive antagonism ; Respiratory function ; Self administration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The recent synthesis of fentanyl derivatives, some of which appear to have novel profiles of pharmacological effects, has provided compelling evidence that μ opioid efficacy might be altered systematically by modifications in the parent compound fentanyl. In the present study a new 4-(heteroanilido)-piperidine, compound 28, was studied for its effects in rhesus monkeys. In self-administration studies compound 28 maintained rates of lever pressing similar to those maintained by alfentanil; the reinforcing effects of compound 28 were attenuated by the opioid antagonist quadazocine. In drug discrimination studies compound 28 did not substitute for the κ agonist ethylketocyclazocine and did substitute for the μ agonist alfentanil. In morphine-treated subjects discriminating between saline and naltrexone, compound 28 did not substitute for naltrexone; however, in morphine-abstinent subjects compound 28 reversed naltrexone lever responding. Moreover, this discriminative stimulus effect in morphine-abstinent subjects was antagonized by naltrexone and by quadazocine in a manner consistent with μ receptor mediation. Compound 28 also was an effective analgesic in a warm-water, tail-withdrawal procedure and it decreased markedly respiratory function. The analgesic effects as well as the respiratory depressant effects of compound 28 were antagonized by quadazocine. Together, these results show compound 28 to be a potent, efficacious μ agonist of similar potency to alfentanil. Large differences in apparent efficacy at μ receptors between compound 28 and another compound in this series (mirfentanil), clearly demonstrate that, within this chemical family, small chemical changes can confer significant differences in pharmacologic effect.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02245876
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  • 2
    Electronic Resource
    Electronic Resource
    The discriminative stimulus effects of naloxone and naltrexone in morphine-treated rhesus monkeys: comparison of oral and subcutaneous administration (1999)
    Springer
    Psychopharmacology 144 (1999), S. 131-136 
    Details
    ISSN: 1432-2072
    Keywords: Key words Naloxone ; Naltrexone ; Rhesus monkey ; Drug discrimination ; Oral ; SC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract   Rationale: Opioid antagonists are used to reverse the toxic effects of opioids, to diagnose opioid dependence and to treat opioid and other (alcohol) drug abuse. Objectives: This study compared the discriminative stimulus effects of two opioid antagonists (naloxone and naltrexone), after parenteral and oral administration. Methods: The discriminative stimulus effects of naloxone and naltrexone were evaluated every 15 min over a 2-h period in four morphine-treated (3.2 mg/kg per day) rhesus monkeys discriminating between subcutaneous (SC) injections of naltrexone (0.01 or 0.032 mg/kg) and saline, while responding under a fixed-ratio 5 schedule of stimulus shock termination. Results: Within 15 min of SC administration, naloxone and naltrexone produced greater than 90% drug-appropriate responding at doses of 0.032 and 0.01 mg/kg, respectively. The largest dose of naloxone (3.2 mg/kg) administered orally produced 82% drug-appropriate responding within 90 min; the same dose of naltrexone administered orally produced greater than 90% drug-appropriate responding within 30 min. Although both drugs were at least 100-fold more potent when administered SC, as compared to orally, there was little difference (3-fold) between the potency of naloxone and naltrexone by either route. Conclusions: These results fail to support the view that naloxone has reduced bioavailability after oral administration, as compared to naltrexone, or that its pharmacokinetic profile is particularly advantageous for some therapeutic settings (e.g. Talwin Nx).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002130050985
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  • 3
    Electronic Resource
    Electronic Resource
    In vivo estimates of efficacy at 5-HT1A receptors: effects of EEDQ on the ability of agonists to produce lower-lip retraction in rats (2000)
    Springer
    Psychopharmacology 149 (2000), S. 377-387 
    Details
    ISSN: 1432-2072
    Keywords: Key words 5-HT1A agonist ; Intrinsic activity ; Efficacy ; Irreversible antagonism ; Lower-lip retraction ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Rationale: Maximal responses are often used as a measure of intrinsic activity or efficacy, but cannot be directly equated to efficacy. Using irreversible antagonists, estimates of efficacy can be obtained that may be less dependent on specific conditions. Objectives: To characterize the intrinsic activity of serotonin (5-HT)1A agonists by examining the effects of an irreversible antagonist on their ability to produce 5-HT1A receptor-mediated responses. Methods: The effects of N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ) on the ability of 5-HT1A agonists to produce lower-lip retraction (LLR) in rats were studied. Results: In the absence of EEDQ, each 5-HT1A agonist produced full effects, the rank order of potency being: S 14506 〉 8-OH-DPAT 〉 buspirone 〉 ipsapirone. EEDQ decreased the number of 5-HT1A binding sites and shifted the dose–response curves (DRCs) of each agonist either to the right or, at higher EEDQ doses, to the right and downward. The manner in which these shifts occurred, however, differed among the compounds. For each agonist, all DRCs obtained after different doses of EEDQ were fitted to models proposed by Furchgott and Black and Leff, and the results indicated the following rank order of efficacy: ipsapirone 〈 buspirone ≈ 8-OH-DPAT 〈 S 14506. 5-HT1A agonist-induced LLR appears to be mediated by 5-HT1A receptors, because the 5-HT1A antagonist, WAY 100635, shifted the agonist DRCs to the right in a parallel and dose-related manner, with pA2 values ranging from 7.8 to 8.1. Moreover, pretreatment with WAY 100635 protected against the antagonist activity of EEDQ. Conclusions: The results suggest that the effects of EEDQ on the ability of 5-HT1A agonists to produce LLR in rats may be useful to obtain estimates of their apparent efficacy at 5-HT1A receptors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002130000374
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  • 4
    Electronic Resource
    Electronic Resource
    Repeated administration of flumazenil does not alter its potency in modifying schedule-controlled behavior in chlordiazepoxide-treated rhesus monkeys (1997)
    Springer
    Psychopharmacology 131 (1997), S. 64-70 
    Details
    ISSN: 1432-2072
    Keywords: Key words Chlordiazepoxide ; Flumazenil ; Benzodiazepine ; Dependence ; Rhesus monkeys ; Schedule-controlled behavior
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Previous reports have suggested that the effects of the benzodiazepine antagonist flumazenil diminish over repeated exposure in subjects treated chronically with a benzodiazepine agonist. The current study examined whether the frequency of exposure to flumazenil altered its potency in decreasing rates of responding in monkeys treated with chlordiazepoxide (CDP). Three monkeys responded under a multiple fixed ratio (FR10:FR10) schedule of food presentation and stimulus-shock termination (SST). In untreated monkeys, flumazenil (0.1–3.2 mg/kg) had no effect in either component. After 2 weeks of treatment with 32.0 mg/kg per day of CDP, flumazenil decreased response rates in the food component, with a dose of 3.2 mg/kg decreasing rates to 10% of control; rates in the SST component were not altered by flumazenil. When flumazenil dose-effect curves were redetermined at 28-, 14-, 7-, 4-, 2- or 1-day intervals, there was no further change in the potency of flumazenil in decreasing food-maintained responding. When CDP treatment was terminated, the potency of flumazenil recovered to pre-CDP values within 23 days. These results suggest that dependence develops to CDP, since changes in the potency of flumazenil co-varied with CDP treatment. Moreover, it does not appear as though results from previous reports, that showed a diminished response to frequently-administered flumazenil, can be generalized to all conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002130050266
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  • 5
    Electronic Resource
    Electronic Resource
    The rate-decreasing effects of fentanyl derivatives in pigeons before, during and after chronic morphine treatment (1998)
    Springer
    Psychopharmacology 137 (1998), S. 67-73 
    Details
    ISSN: 1432-2072
    Keywords: Key words Tolerance ; Cross-tolerance ; Dependence ; Mirfentanil ; Opioid ; Non-opioid ; Morphine ; Fentanyl ; OHM3463 ; OHM3295
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Mirfentanil is a fentanyl derivative with non-opioid actions, including non-opioid antinociceptive effects in rhesus monkeys. The current study examined the rate-altering effects of mirfentanil and several other compounds in pigeons to assess: 1) the opioid and non-opioid actions of acutely-administered fentanyl derivatives; and 2) the development of cross-tolerance between each of these compounds and morphine. Seven pigeons responded under a fixed-ratio 20 (FR20) schedule of food delivery. In untreated pigeons, fentanyl, morphine, naltrexone, ketamine and three fentanyl derivatives (mirfentanil, OHM3463 and OHM3295) decreased rates of key pecking in a dose-related manner. Naltrexone (0.1–1.0 mg/kg) attenuated the effects of OHM3463 and not mirfentanil or OHM3295, suggesting non-opioid mediation of the rate-decreasing effects for the latter two fentanyl derivatives. Subjects were treated daily with morphine for 9 weeks, up to a dose of 100 mg/kg per day, during which time the dose-effect curves for morphine, fentanyl and OHM3463 shifted rightward 6-, 10- and 2-fold, respectively, indicating the development of tolerance to morphine and cross-tolerance to fentanyl and OHM3463. Dose-effect curves for ketamine, OHM3295 and mirfentanil were not shifted to the right during morphine treatment, and the dose-effect curve for naltrexone was shifted leftward 180-fold. To the extent that rate-decreasing effects are predictive of antinociceptive effects, these data suggest that some fentanyl derivatives might be useful therapeutics under conditions where tolerance develops to morphine-like opioids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002130050594
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  • 6
    Electronic Resource
    Electronic Resource
    Studies on benzodiazepines and opioids administered alone and in combination in rhesus monkeys: ventilation and drug discrimination (1998)
    Springer
    Psychopharmacology 137 (1998), S. 164-174 
    Details
    ISSN: 1432-2072
    Keywords: Key words Benzodiazepine ; Opioid ; Ventilation ; Drug discrimination ; Rhesus monkeys
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Benzodiazepines and opioids are co-administered recreationally as well as clinically; in the current study, the ventilatory-depressant and discriminative stimulus effects of several benzodiazepines and opioids were examined alone and in combination in order to evaluate any interaction between agonists from these pharmacological classes. The benzodiazepines alprazolam, diazepam, flunitrazepam, lorazepam, midazolam and triazolam and the opioids morphine and fentanyl decreased ventilation (VE) in monkeys breathing either air or 5% CO2 in air, although decreases in ventilation produced by opioids were greater in magnitude than decreases produced by benzodiazepines. Flumazenil antagonized the ventilatory-depressant effects of flunitrazepam and triazolam and not those of fentanyl; naltrexone antagonized the ventilatory-depressant effects of fentanyl and not those of flunitrazepam or triazolam. Interactions between the ventilatory-depressant effects of agonists from the two classes were less than additive. In monkeys receiving 3.2 mg/kg per day of morphine and discriminating 0.01 mg/kg naltrexone, neither flunitrazepam nor triazolam substituted for naltrexone; in morphine-deprived monkeys, morphine, and not flunitrazepam or triazolam, reversed naltrexone-lever responding. Moreover, benzodiazepines did not modify the discriminative stimulus effects of naltrexone in morphine-treated monkeys or of morphine in morphine-deprived monkeys. In contrast to studies showing synergism between benzodiazepines and opioids, the current study suggests that, under some conditions, combinations of these drugs can be administered without enhancing the ventilatory-depressant effects of either class of drugs or the discriminative stimulus effects of opioids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002130050606
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