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Article
Evidence for a role of 5-HT2C receptors in the motor aspects of performance, but not the efficacy of food reinforcers, in a progressive ratio schedule
5-Hydroxytryptamine2C (5-HT2C) receptor agonists reduce the breakpoint in progressive ratio schedules of reinforcement, an effect that has been attributed to a decrease of the efficacy of positive reinforcers. Ho...
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Article
Open AccessEffects of SKF-83566 and haloperidol on performance on progressive ratio schedules maintained by sucrose and corn oil reinforcement: quantitative analysis using a new model derived from the Mathematical Principles of Reinforcement (MPR)
Mathematical models can assist the interpretation of the effects of interventions on schedule-controlled behaviour and help to differentiate between processes that may be confounded in traditional performance ...
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Article
Nucleus accumbens and delay discounting in rats: evidence from a new quantitative protocol for analysing inter-temporal choice
There is evidence that the core of the nucleus accumbens (AcbC) is involved in inter-temporal choice behaviour.
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Article
Open AccessAttenuation of the effects of d-amphetamine on interval timing behavior by central 5-hydroxytryptamine depletion
Interval timing in the free-operant psychophysical procedure is sensitive to the monoamine-releasing agent d-amphetamine, the D2-like dopamine receptor agonist quinpirole, and the D1-like agonist 6-chloro-2,3,4,5...
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Article
Open AccessEffect of quinolinic acid-induced lesions of the nucleus accumbens core on performance on a progressive ratio schedule of reinforcement: implications for inter-temporal choice
The nucleus accumbens core (AcbC) is believed to contribute to the control of operant behaviour by reinforcers. Recent evidence suggests that it is not crucial for determining the incentive value of immediatel...
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Article
Evidence for the sensitivity of operant timing behaviour to stimulation of D1 dopamine receptors
Temporal differentiation of operant behaviour is sensitive to dopaminergic manipulations. Previous studies using the fixed-interval peak procedure implicated D2-like dopamine receptors in these effects. However, ...
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Article
Arousal and the pupil: why diazepam-induced sedation is not accompanied by miosis
There is a close relationship between arousal and pupil diameter, decrease in the level of arousal being accompanied by constriction of the pupil (miosis), probably reflecting the attenuation of sympathetic ou...
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Article
Effects of quinolinic acid-induced lesions of the nucleus accumbens core on inter-temporal choice: a quantitative analysis
There is evidence that lesions of the nucleus accumbens core (AcbC) promote preference for smaller earlier reinforcers over larger delayed reinforcers in inter-temporal choice paradigms. It is not known whethe...
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Article
Effect of quinpirole on timing behaviour in the free-operant psychophysical procedure: evidence for the involvement of D2 dopamine receptors
Operant timing behaviour is sensitive to dopaminergic manipulations. It has been proposed that this effect is mediated principally by D2-like dopamine receptors. However, we recently found that the effect of d-am...
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Article
Tolerance to the effect of 2,5-dimethoxy-4-iodoamphetamine (DOI) on free-operant timing behaviour: interaction between behavioural and pharmacological mechanisms
The psychostimulant d-amphetamine, the D2/3 dopamine receptor agonist quinpirole and the 5-HT2 receptor agonist 2,5-dimethoxy-4-iodoamphetamine (DOI) have similar effects on free-operant timing behaviour. There i...
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Article
Effects of d-amphetamine and DOI (2,5-dimethoxy-4-iodoamphetamine) on timing behavior: interaction between D1 and 5-HT2A receptors
The dopamine-releasing agent d-amphetamine and the 5-HT2 receptor agonist 2,5-dimethoxy-4-iodoamphetamine (DOI) have similar effects on free-operant timing behavior. The selective D1 dopamine receptor antagonist ...
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Article
Comparison of pramipexole and amisulpride on alertness, autonomic and endocrine functions in healthy volunteers
In a previous study in healthy volunteers, the anti-Parkinsonian drug pramipexole caused sedation and pupil dilatation, consistent with the stimulation of inhibitory D2/D3 autoreceptors on the ventral tegmental a...
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Article
Evidence for a role of D1 dopamine receptors in d-amphetamine’s effect on timing behaviour in the free-operant psychophysical procedure
Temporal differentiation of operant behaviour is sensitive to dopaminergic manipulations. Studies using the fixed-interval peak procedure implicated D2 dopamine receptors in these effects. Less is known about the...
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Article
Why patients with Alzheimer’s disease may show increased sensitivity to tropicamide eye drops: role of locus coeruleus
Patients suffering from Alzheimer’s disease (AD) may show increased sensitivity to tropicamide, a muscarinic cholinoceptor antagonist. AD is associated with a severe loss of noradrenergic neurones in the locus...
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Article
Does modafinil activate the locus coeruleus in man? Comparison of modafinil and clonidine on arousal and autonomic functions in human volunteers
Modafinil is a wakefulness-promoting drug which is likely to activate some wakefulness-promoting and/or inhibit sleep-promoting neurones in the brain. The locus coeruleus (LC) is a wakefulness-promoting noradr...
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Article
Effects of quipazine and m-chlorophenylbiguanide (m-CPBG) on temporal differentiation: evidence for the involvement of 5-HT2A but not 5-HT3 receptors in interval timing behaviour
Temporal differentiation refers to animals’ ability to regulate their behaviour during an ongoing interval. Striatal dopaminergic mechanisms are purported to be involved in temporal differentiation, and recent...
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Article
Comparison of the effects of clozapine and 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) on progressive ratio schedule performance: evidence against the involvement of 5-HT1A receptors in the behavioural effects of clozapine
Performance on progressive ratio schedules has been proposed as a means of assessing the effects of drugs on the efficacy of reinforcers. A mathematical model (Killeen PR (1994) Mathematical principles of rein...
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Article
Quantitative analysis of the effects of some “atypical” and “conventional” antipsychotics on progressive ratio schedule performance
Performance on progressive ratio schedules has been proposed as a means of assessing the effects of drugs on the value or “efficacy” of reinforcers. A mathematical model affords a basis for quantifying the eff...
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Article
Effects of fenfluramine on free-operant timing behaviour: evidence for involvement of 5-HT2A receptors
Temporal differentiation in the free-operant psychophysical procedure is sensitive to the 5-hydroxytryptamine (5-HT)1A receptor agonist 8-hydroxy-2-(di-n-propylamino)-tetralin (8-OH-DPAT) and the 5-HT2 receptor a...
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Article
Effects of orbital prefrontal cortex dopamine depletion on inter-temporal choice: a quantitative analysis
Lesions of the orbital prefrontal cortex (OPFC) can cause pathologically impulsive behaviour in humans. Inter-temporal choice behaviour (choice between reinforcers differing in size and delay) has been propose...
