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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Psychopharmacology 87 (1985), S. 207-211 
    ISSN: 1432-2072
    Schlagwort(e): d-Amphetamine ; Operant behaviour ; Variable-interval schedules ; Herrnstein's equation ; Rat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Dose-response curves were obtained for the effects of d-amphetamine sulphate (0.1–3.2 mg/kg) on the operant performance of rats in variable-interval 4-min and variableinterval 20-min schedules of reinforcement. Response rates maintained under variable-interval 4-min were suppressed in a dose-dependent manner. Response rates maintained under variable-interval 20-min schedules tended to be elevated by low doses and suppressed by higher doses. The degree of response rate suppression was greater in the case of the variable-interval 4-min schedule. The results are consistent with the previously reported effect of d-amphetamine on the values of the two constants of Herrnstein's (1970) equation: the drug reduces the reinforcement frequency needed to maintain the half-maximum response rates (K h) and lowers the maximum response rate (R max) (Bradshaw et al. 1981 b). It is suggested that the effects of d-amphetamine on operant performance may involve two processes: an enhancement of motivation and a reduction of the capacity to respond.
    Materialart: Digitale Medien
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  • 2
    ISSN: 1432-2072
    Schlagwort(e): Operant behaviour ; Variable-interval schedules ; Pentobarbitone ; Herrnstein's equation ; Rats
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Six rats were exposed to a series of variable-interval schedules of reinforcement, each schedule specifying a different reinforcement frequency. The effects of two doses of pentobarbitone (24.16 and 40.27 μmol/kg) upon performance maintained under each schedule were examined. The data were analyzed in terms of the goodness of fit of Herrnstein's (1970) equation. Under control conditions (so injection or injection of vehicle alone) response rate was an increasing negatively accelerated function of reinforcement frequency, the data obtained from each rat conforming closely to Herrnstein's equation. In the presence of pentobarbitone there was a reduction in the value of R max (the theoretical maximum response rate) in all six rats. The effect of pentobarbitone upon the value of K H (the reinforcement frequency needed to obtain the half-maximal response rate) differed between animals, the value being increased in some rats and decreased in others. This was shown to reflect a systematic relationship between the baseline value of K H and the change in K H produced by pentobarbitone, high baseline values being associated with reductions, and low baseline values with elevations, in the presence of the drug. The data were also analyzed using conventional rate-dependency analysis. In some animals there was a tendency for lower response rates to be suppressed to a greater degree than higher rates, while the reverse was true in other animals. In general, rate-dependency functions provided poor descriptions of the data obtained from individual subjects.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Psychopharmacology 91 (1987), S. 239-243 
    ISSN: 1432-2072
    Schlagwort(e): Pimozide ; d-Amphetamine ; Operant behaviour ; Variable-interval schedules ; Rat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The interaction between pimozide (a selective D2-dopamine receptor antagonist) and d-amphetamine on the operant performance of rats maintained under variable-interval schedules of positive reinforcement was examined. In Experiment 1, eight rats responded under variable-interval 30-s and variable-interval 300-s. Pimozide (0.0625, 0.125, 0.25, 0.5 mg/kg) suppressed performance maintained under both schedules in a dose-dependent manner, the degrees of suppression being equivalent in the two schedules. In Experiment 2, 12 rats responded under the same schedules. d-Amphetamine (0.1–3.2 mg/kg) suppressed performance under both schedules, the degree of suppression being somewhat greater in the case of variable-interval 30-s. Pre-treatment with pimozide (0.0625, 0.125 mg/kg) significantly attenuated the suppressant effect of d-amphetamine under both schedules. It is suggested that D2-dopamine receptors may be involved in mediating the suppressant effect of d-amphetamine on operant behaviour.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 4
    ISSN: 1432-2072
    Schlagwort(e): DSP4 ; Noradrenaline ; d-Amphetamine ; Operant behaviour ; Variable-interval schedules ; Rat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The effect of d-amphetamine (0.1–3.2 mg/kg) on performance in variable-interval 1-min and variable-interval 12-min schedules of positive reinforcement was examined in ten rats treated with the selective noradrenaline neurotoxin DSP4 and 12 control rats. In the control group d-amphetamine had a dose-dependent suppressant effect on response rates maintained under variable-interval 1-min; under variable-interval 12-min, response rates were increased by low doses and suppressed by higher doses of the drug. In the case of both schedules, lower doses of d-amphetamine were more suppressant and higher doses less suppressant in the DSP4-treated group than in the control group. The levels of noradrenaline in the parietal cortex, hippocampus and cerebellum (determined by high-performance liquid chromatography) were reduced to approximately 15% of control levels in the DSP4-treated rats. The results indicate that treatment with DSP4 attenuated both the facilitatory and the suppressant effects of d-amphetamine on variable-interval performance. A formal model couched in terms of Herrnstein's (1970) equation is put forward to account for these results. It is suggested that the noradrenergic pathways emanating from the locus caeruleus are involved in both the facilitatory and suppressant effects of d-amphetamine on operant behaviour.
    Materialart: Digitale Medien
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