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  • Dopamine  (4)
  • Cocaine  (2)
  • Rat  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Psychopharmacology 85 (1985), S. 80-86 
    ISSN: 1432-2072
    Keywords: Conditioned suppression ; Drug stimuli ; Stimulus control ; Overshadowing ; Classical conditioning ; Operant behavior ; Drugs ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Rats were trained to press a lever under a variable-interval (VI) schedule of water reinforcement. After stable responding had developed, a 4.5-KHz tone (CS) was conditioned classically to a 2.5-mA electric shock (US) in groups of animals which had been given various psychoactive drugs or saline. Twenty-four hours later, a stimulus generalization test was conducted in the absence of drug; during this session, tones that varied in frequency around 4.5 KHz were presented while the animals were responding under the VI schedule. In animals conditioned under saline, all tones (non-differentially) suppressed responding which, however, recovered gradually over time. This suppressive effect was eliminated by lysergic acid diethylamide (LSD; 0.2 and 0.32 mg/kg), cocaine (20 mg/kg), diazepam (2.5 mg/kg), lisuride (0.08 mg/kg), mescaline (20 mg/kg) and 5-methoxy-N,N-dimethyltryptamine (4 mg/kg), and was attenuated by amphetamine (4 mg/kg), pentobarbital (15 mg/kg) and morphine (4 mg/kg). Atropine (10 mg/kg), scopolamine (1 mg/kg), clonazepam (0.5 mg/kg), and chlorpromazine (4 mg/kg) did not alter the suppressive effect of the tone. The serotonin antagonist BC-105 (6 mg/kg) reversed the effect of 0.2 mg/kg of LSD. These results suggest (1) that drug-induced stimuli may “overshadow” other (e.g., external) stimuli during classical conditioning and, (2) that drugs might affect behavior by altering processes (stimulus control or others) that do not simultaneously involve response or motor control.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-2072
    Keywords: Pentazocine ; Morphine ; Levorphanol ; Phenazocine ; Opiates ; Opiate receptors ; Dopamine ; (DA) receptors ; Antinociception ; Analgesia ; Discrimination ; Rats
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The hypothesis that the antinociceptive effects of pentazocine, a mixed agonist-antagonist opiate of the benzomorphan class, are mediated by a dual opiate-dopaminergic mechanism was tested using a two-choice procedure in which rats were required to discriminate the presence or absence of shock. The results showed that pentazocine decreased shock sensitivity and speed of responding, effects that were qualitatively similar to those of morphine. However, while the antinociceptive effect of both pentazocine and morphine could be antagonized by opiate receptor blockade, that of pentazocine, but not of morphine, could also be antagonized by dopamine receptor blockade. Observations with levorphanol and phenazocine suggested further that dopamine, as well as opiate receptor agonism may be characteristic of the benzomorphans.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Psychopharmacology 73 (1981), S. 110-115 
    ISSN: 1432-2072
    Keywords: Fenfluramine ; Hallucinogens ; LSD ; Lisuride ; Quipazine ; MK-212 ; p-Chloroamphetamine ; p-Chlorophenylalanine ; d-Amphetamine ; Cocaine ; Fluoxetine ; Serotonin ; Serotonin agonists ; Serotonin antagonists ; Drug discrimination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Rats were trained to discriminate fenfluramine (1.0 mg/kg) from saline in a two-lever drug discrimination task. The dose-response curve for this discrimination was orderly with an ED50 of about one-half of the training dose (0.52 mg/kg). In substitution tests, indirect (p-chloroamphetamine) and direct (quipazine, MK-212, lisuride) serotonin (5-HT) agonists substituted for fenfluramine. Since none of these compounds have been reported to be hallucinogenic and the potent hallucinogen LSD did not substitute completely, it was suggested that the discriminative stimulus properties of fenfluramine are not related to its ability to produce hallucinations in humans. The fenfluramine cue, like the quipazine cue, was antagonized by the 5-HT antagonists cyproheptadine and methiothepin. Unlike quipazine, fenfluramine was also partially antagonized by the 5-HT uptake inhibitor, fluoxetine, and the 5-HT synthesis inhibitor, p-chlorophenylalanine. Thus, the fenfluramine cue differs from that of quipazine in that it is mediated via indirect actions on 5-HT receptors. Since the indirect dopamine (DA) agonist d-amphetamine failed to substitute and the DA antagonist haloperidol failed to block the fenfluramine cue, a mediating role for DA was not indicated. Another indirect DA agonist, cocaine, substituted partially for fenfluramine, a result which paralleled that seen with fluoxetine. Both of these partial substututions were reduced by cyproheptadine; therefore, it was concluded that these effects may be due to the common ability of cocaine, fluoxetine, and fenfluramine to inhibit 5-HT uptake.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Psychopharmacology 76 (1982), S. 20-25 
    ISSN: 1432-2072
    Keywords: LSD ; Drug discrimination ; Training dose ; Serotonin ; Dopamine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract To assess the effects of training dose on the discriminative stimulus properties of LSD, groups of rats (eight/group) were trained to discriminate each of three doses of LSD (0.02, 0.08 or 0.32 mg/kg) from saline. This was accomplished by using a method of progressively altering dose (“fading”). Dose-response tests revealed that the three LSD cues were specific to the dose used during training and that, as the training dose declined, the slope of the LSD dose-response curve became less steep. Substitution tests with direct serotonin (5-HT) agonists (quipazine, MK-212, 5-methoxy-N,N-dimethyltryptamine) and antagonism tests with central 5-HT antagonists (methiothepin and cyproheptadine) indicated that 5-HT is involved in mediating the in vivo effects of LSD and that training dose co-determines (along with the dose of the test compound) the extent of substitution or antagonism. In addition, substitution tests with the peripherally-active 5-HT agonist 5-methoxytryptamine and 5-HT antagonist xylamidine suggested that the peripheral serotonergic actions of LSD may be involved (in part) in the low dose (0.02 mg/kg) LSD cue. In contrast to 5-HT, dopamine (DA) did not appear to be involved in the discriminative stimulus properties of LSD, because no significant dose or group effects were seen during tests with the DA agonists apomorphine and d-amphetamine or the DA antagonist haloperidol.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-2072
    Keywords: Cocaine ; Dopamine ; Dopamine receptors ; Drug discrimination ; Drug stimuli ; Receptors ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The involvement of dopamine (DA) receptor subtypes in the behavioral effects of CNS stimulants was studied in rats trained to discriminate occaine from saline. In substitution tests, the stimulus effects of 10mg/kg of this substance generalized tod-amphetamine (0.25–1.0 mg/kg) and the selective D2 against LY-171555 (0.05–0.25 mg/kg); but not to the D1 agonist SKF-38393 (5.0–15.0 mg/kg); in combination tests, the D1 antagonist Sch-23390 (0.0625–0.5 mg/kg) significantly blocked, and the D2 antagonist spiperone (0.25–0.5 mg/kg) partially blocked the cocaine cue. These data suggest that the involvement of DA systems in the behavioral effects of cocaine is more complex than either D1 or D2 receptor activation; for example, the stimulus properties of this substance might involve both D1 and D2 receptor activation.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-2072
    Keywords: Dopamine ; Drug discrimination ; LSD ; Lisuride ; Serotonin ; Three-choice discrimination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The discriminative stimulus properties of (+)-lysergic acid diethylamide (LSD) and lisuride hydrogen maleate (LHM), were compared in a three-choice, water reinforced (FR 20) situation in which rats were required to press one lever following LSD (0.08 mg/kg), a second lever following LHM (0.04 mg/kg), and a third lever following saline. Reliable drug-appropriate responding was established in 72 sessions. Dose-response tests with LSD and LHM indicated that, as dose increased, the per cent of responding on the lever associated with the particular training drug also increased; little or no cross-transfer occurred between LSD and LHM. In generalization tests, the serotonin (5-HT) agonist quipazine substituted for LSD but not LHM while the dopamine (DA) agonist apomorphine mimicked LHM but not LSD; an unrelated compound, pentylenetetrazol (PTZ), produced responding on the saline-appropriate lever. In combination tests, 5-HT antagonists (e.g., BC-105 and low doses of pirenperone) blocked responding on the LSD lever while DA antagonists (e.g., haloperidol and much higher doses of pirenperone) blocked LHM-appropriate responding. These data suggest that the three-lever (D-D-N) procedure is similar to, but can be more sensitive than the two-lever (D-N) procedure (because it can differentiate between LSD and LHM); they therefore at least partially support the hypothesis that three-choice discriminations can be conceptualized as two separate, two-choice (D-N) discriminations (Jarbe and Swedberg 1982). The results also confirm suggestion that the stimulus effects of LSD and LHM are mediated by different mechanisms; the primary action of LSD is serotonergic (5-HT2), while that of LHM is dopaminergic (White 1986).
    Type of Medium: Electronic Resource
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