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  • Progressive ratio  (2)
  • 1,5-bisphosphate carboxylase  (1)
  • 1
    Digitale Medien
    Digitale Medien
    A point mutation in the N-terminus of ribulose-1,5-bisphosphate carboxylase affects ribulose-1,5-bisphosphate binding (1991)
    Springer
    Planta 184 (1991), S. 35-39 
    Details
    ISSN: 1432-2048
    Schlagwort(e): Ribulose ; 1,5-bisphosphate carboxylase ; Gene mutation (N-terminus) ; Substrate affinity (ribulose-1,5-bisphosphate)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Mutagenesis in vitro of the gene encoding the large subunit of ribulose-1,5-bisphosphate carboxylase/ oxygenase (EC 4.1.1.39) from Anacystis nidulans was used to generate novel enzymes. Two conserved residues, threonine 4 and lysine 11 in the N-terminus were changed. The substitution of threonine 4 with serine or valine had little effect on the kinetic parameters. The substitution of lysine 11 with leucine, which is non-polar, increased the K m for ribulose-1,5-bisphosphate from 82 to 190 μM but its replacement with glutamine, which has polar properties, had no appreciable effect.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00208233
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  • 2
    Digitale Medien
    Digitale Medien
    Pre-exposure of rats to amphetamine sensitizes self-administration of this drug under a progressive ratio schedule (1998)
    Springer
    Psychopharmacology 135 (1998), S. 416-422 
    Details
    ISSN: 1432-2072
    Schlagwort(e): Key words Sensitization ; d-Amphetamine ; Drug self-administration ; Progressive ratio ; Incentive motivation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract  Two groups of male rats were tested to determine whether pre-exposure to d-amphetamine would enhance the motivation to self-administer the drug under a progressive ratio schedule of reinforcement. In the first phase of the experiment, one group of rats received d-amphetamine (2 mg/kg IP), while a second group received saline on alternate days for a total of ten injections. Following a 21-day drug withdrawal period, behavioral sensitization was confirmed by a significant increase in amphetamine-induced stereotypy in the d-amphetamine-pretreated group, relative to the saline-pretreated group. In the second phase of the study, all rats were implanted with chronic jugular catheters and trained to self-administer d-amphetamine (0.2 mg/kg per infusion) under a fixed-ratio schedule of reinforcement. The progressive ratio paradigm was then imposed for 7 consecutive days; d-amphetamine-pretreated rats attained significantly higher break points than saline-pretreated animals. These data suggest that pre-exposure to d-amphetamine may enhance the motivation to self-administer this drug.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002130050530
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  • 3
    Digitale Medien
    Digitale Medien
    Withdrawal following repeated exposure to d-amphetamine decreases responding for a sucrose solution as measured by a progressive ratio schedule of reinforcement (1999)
    Springer
    Psychopharmacology 141 (1999), S. 99-106 
    Details
    ISSN: 1432-2072
    Schlagwort(e): Key words Anhedonia ; Amphetamine ; Depression ; Progressive ratio ; Psychostimulant ; Rat ; Sucrose solution ; Withdrawal
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Numerous studies have shown that withdrawal from sustained high doses of psychostimulant drugs such as cocaine or d-amphetamine produces depressive-like symptoms in both rats and humans. The majority of experiments with rodents have assessed the effects of amphetamine withdrawal on reinforcing electrical self-stimulation in different brain regions, but relatively few have examined effects on responding for natural reinforcers. In the present study, two groups of mildly food and water deprived male rats were trained to respond on a lever for a 4% sucrose solution under a progressive ratio schedule of reinforcement. One group was subsequently administered a 4-day regimen of injections of increasing doses of d-amphetamine based on a schedule shown previously to reduce self-stimulation behaviour. Break points were significantly reduced for up to 4 days after the termination of drug administration, suggesting a decreased motivation to obtain the natural reward. A further experiment demonstrated that the identical drug regimen produced no effect upon consumption of the 4% sucrose solution when it was freely available. These results demonstrate that the progressive ratio procedure may be a useful technique for evaluating changes in motivation for natural reinforcing stimuli following withdrawal from psychostimulant drugs.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002130050812
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