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  • 1
    Electronic Resource
    Electronic Resource
    Depletion of unilateral striatal dopamine impairs initiation of contralateral actions and not sensory attention (1985)
    [s.l.] : Nature Publishing Group
    Nature 313 (1985), S. 679-682 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] In procedure (1), two groups of rats were trained to hold their heads in a central hole until an eccentric visual stimulus was presented to one or other side of the head. The two groups were required to report the presence of the light either by moving their heads towards it (SAME group, n = 6) or ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/313679a0
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  • 2
    Electronic Resource
    Electronic Resource
    A comparison of the effects of amphetamine, apomorphine and white noise on response switching in the rat (1989)
    Springer
    Psychopharmacology 97 (1989), S. 238-242 
    Details
    ISSN: 1432-2072
    Keywords: Amphetamine ; Apomorphine ; Arousal ; Behaviour pattern
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effects of d-amphetamine, apomorphine and white noise on response switching in the rat were examined using a schedule of reinforcement which resulted in the subjects displaying a range of different probabilities of switching. The procedure was analogous to the use of a fixed interval schedule of reinforcement for examining the ratedependent effects of drugs. d-Amphetamine (0.4–4.0 mg/kg) increased response switching in a manner dependent both upon the dose of drug and the baseline probability of switching. Apomorphine (0.01–0.3 mg/kg) increased switching in a manner which depended upon dose but which was independent of the baseline probability of switching. Neither drug increased response rate, although both drugs reduced response rate at the highest doses. In contrast, continuous white noise (85–105 dB) increased response rate without affecting switching. The results indicate that different activating stimuli may have qualitatively different effects on behaviour.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00442257
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  • 3
    Electronic Resource
    Electronic Resource
    Varieties of impulsivity (1999)
    Springer
    Psychopharmacology 146 (1999), S. 348-361 
    Details
    ISSN: 1432-2072
    Keywords: Key words Impulsivity ; Personality ; Serotonin ; Behaviour
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The concept of impulsivity covers a wide range of ”actions that are poorly conceived, prematurely expressed, unduly risky, or inappropriate to the situation and that often result in undesirable outcomes”. As such it plays an important role in normal behaviour, as well as, in a pathological form, in many kinds of mental illness such as mania, personality disorders, substance abuse disorders and attention deficit/hyperactivity disorder. Although evidence from psychological studies of human personality suggests that impulsivity may be made up of several independent factors, this has not made a major impact on biological studies of impulsivity. This may be because there is little unanimity as to which these factors are. The present review summarises evidence for varieties of impulsivity from several different areas of research: human psychology, psychiatry and animal behaviour. Recently, a series of psychopharmacological studies has been carried out by the present author and colleagues using methods proposed to measure selectively different aspects of impulsivity. The results of these studies suggest that several neurochemical mechanisms can influence impulsivity, and that impulsive behaviour has no unique neurobiological basis. Consideration of impulsivity as the result of several different, independent factors which interact to modulate behaviour may provide better insight into the pathology than current hypotheses based on serotonergic underactivity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00005481
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  • 4
    Electronic Resource
    Electronic Resource
    The pharmacology of impulsive behaviour in rats VI: the effects of ethanol and selective serotonergic drugs on response choice with varying delays of reinforcement (1999)
    Springer
    Psychopharmacology 146 (1999), S. 413-421 
    Details
    ISSN: 1432-2072
    Keywords: Key words Ethanol ; Serotonin ; Delayed reinforcement ; Self-control ; Impulsivity ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Rationale: Tolerance to delay of reinforcement has been proposed as an important facet of self-control in both animals and man. Poor self-control, leading to impulsive behaviour, can be a major problem if it reaches pathological levels. Objectives: The effects of five serotonergic drugs were compared to those of ethanol on a procedure for measuring tolerance to delay of reinforcement in rats in order to elucidate further the role of the serotonin systems in the regulation of impulsive behaviour. Methods: Rats were trained to choose between a single food pellet (small reinforcer) delivered immediately or five food pellets (large reinforcer) delivered after programmed delays. At the start of each session, there was no delay between the response and delivery of the large reinforcer, but this was increased stepwise during the session to delays of 10, 20, 40 and 60 s. Results: The rats showed consistent preference for the larger reinforcer when it was not delayed but showed a shift in preference as the session continued, so that they preferred the small reinforcer when the large was delayed by 40 or 60 s. Ethanol at a dose of 1.0 g/kg produced a significance increase in preference for the small, immediate reinforcer throughout the session, although there were marked individual differences in the size of the effect. A similar, but somewhat smaller effect was seen with the 5-HT2 agonist, DOI, at a dose of 1.0 mg/kg. In contrast, the 5-HT1A agonist, 8-OH-DPAT (0.3 mg/kg) reduced preference for the large reinforcer at the start of the session, and reduced preference for the small reinforcer at the end of the session, i.e. produced a regression to indifference. Lower doses of these three drugs, and treatment with the 5-HT receptor subtype selective antagonists WAY-100635 (5-HT1A: 0.01–0.1 mg/kg), ritanserin (5-HT2: 0.1 and 0.3 mg/kg) and MDL-72222 (5-HT3: 1.0 and 3.0 mg/kg) had no significant effects on reinforcer choice. Conclusion: These data show that ethanol and DOI increase preference for the immediate reinforcer, which can be construed as evidence of an increase in impulsive behaviour (reduction in self control), whereas selective blockade of the 5-HT1A, 5-HT2 or 5-HT3 receptors using selective antagonists does not affect self-control.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00005486
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  • 5
    Electronic Resource
    Electronic Resource
    The pharmacology of impulsive behaviour in rats VII: the effects of serotonergic agonists and antagonists on responding under a discrimination task using unreliable visual stimuli (1999)
    Springer
    Psychopharmacology 146 (1999), S. 422-431 
    Details
    ISSN: 1432-2072
    Keywords: Key words Reaction time ; Impulsivity ; Serotonin ; 8-OH-DPAT ; DOI
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Rationale: The serotonergic systems have been implicated in the pathological impulsive behaviour on the basis of both clinical and preclinical data. However, impulsivity is probably made up of several independent factors, and the involvement of the diverse regulatory mechanisms of the serotonergic systems has not been widely studied. Objective: The influence of a range of serotonergic agents on impulsivity was examined using a procedure designed to test the dimension of impulsivity termed ”reflection-impulsivity” in rats. Methods: An operant procedure was used in which the need to wait before responding was made explicit by using a signal which increased in predictive value the longer the subject waited before responding. First, the rats learned that a light signal indicated the availability of a food reinforcer if one of two levers was pressed. In the test procedure, on each trial, when the light was turned on it was only 50% likely to indicate the ”correct” lever. After a brief interval it was turned off and on again, this time with a slightly higher probability (〉50%) of indicating the correct lever. Over a period of a few seconds the probability that the light indicated the correct lever increased to almost 100%. Thus a quick response to the light would result in many errors, whereas a slow response could always result in food delivery. Once trained the rats were treated with a series of drugs: citalopram, (selective serotonin reuptake inhibitor), p-chloramphetamine (PCA, serotonin releaser), 8-OH-DPAT (5-HT1A agonist), RU24969 (primarily a 5-HT1B receptor agonist), DOI, (5-HT2 agonist), WAY-100,635 (5-HT1A antagonist), ritanserin (5-HT2 antagonist), and MDL-72222, (5-HT3 antagonist). Results: Of the test compounds, PCA, DOI and 8-OH-DPAT increased reaction times, whereas ritanserin reduced them. Citalopram and WAY-100,635 had no significant effects, RU-24969 appeared to disrupt responding, and MDL-72222 reduced premature responses and the number of short reaction times. Conclusions: Since agonists at the 5-HT1A and 5-HT2 receptors both reduced impulsivity in this procedure, these data suggest that serotonin may promote ”reflection” in this procedure via stimulation of these receptor subtypes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00005487
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  • 6
    Electronic Resource
    Electronic Resource
    Effects of repeated treatment with 5-HT1A agonists on active avoidance responding in the rat (1993)
    Springer
    Psychopharmacology 112 (1993), S. 45-54 
    Details
    ISSN: 1432-2072
    Keywords: Serotonin agonist ; 8-OH-DPAT ; Flesinoxan ; Ipsapirone ; Buspirone ; Haloperidol ; Active avoidance ; Rats ; Repeated treatment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The behavioural effects of the serotonin 1A receptor (5-HT1A) agonist anxiolytics are generally examined after acute administration. The present study examined the effects of these substances during repeated treatment in the two-way active avoidance (Conditioned Avoidance Response, CAR) procedure. Previously it has been found that the prototypical 5-HT1A receptor agonist, 8-OH-DPAT, increases avoidance, apparently by increasing general activity, after repeated administration but not on acute administration. In the present study, it was demonstrated that this increase in activity can be blocked by the 5-HT1A receptor antagonists (−)alprenolol (also beta adrenergic antagonist) and (S)-UH-301, but not by the non-selective 5-HT antagonist metergoline. The relatively full 5-HT1A agonist, flesinoxan, and the partial 5-HT1A agonist, ipsapirone, had qualitatively similar effects to 8-OH-DPAT, although the effect of ipsapirone was clearly smaller in magnitude. Buspirone, the 5-HT1A partial agonist/dopamine D2 antagonist, markedly decreased activity, and thus avoidance of the shocks, in a manner similar to the antipsychotic drug, haloperidol. However, when the hypothermic effects of these compounds were investigated after acute administration, buspirone induced a strong hypothermic response in rats, like 8-OH-DPAT, whereas haloperidol had no effect. With the exception of buspirone, the effectiveness of these compounds in increasing activity in the CAR test appears to be related to their agonist efficacy at the 5-HT1A receptor. Similarities between the effects of these compounds and previously reported results with serotonin-depleting agents (Tenen 1967; Breese et al. 1974) suggest that the net effect of 5-HT1A agonists after repeated administration is to produce a functional reduction in 5-HT activity. The activity suppressing action of buspirone indicates that the dopamine antagonist activity of buspirone predominates in this procedure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02247362
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  • 7
    Electronic Resource
    Electronic Resource
    The pharmacology of impulsive behaviour in rats III: the effects of amphetamine, haloperidol, imipramine, chlordiazepoxide and ethanol on a paced fixed consecutive number schedule (1998)
    Springer
    Psychopharmacology 138 (1998), S. 295-304 
    Details
    ISSN: 1432-2072
    Keywords: Key words Impulsivity ; Rat ; Imipramine ; Ethanol ; Haloperidol ; Chlordiazepoxide ; Amphetamine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The behavioural trait of impulsivity may be made up of different components, including rapid decision making, intolerance to the delay of reward and a tendency to terminate chains of responses prematurely. It has been proposed to measure the last of these in rats using fixed consecutive number (FCN) schedules. The present study uses a modified version of the FCN procedure in which responding was paced by retracting the response lever for short periods between presses. In this way, the experimenter could control the maximum rate of responding. The procedure was made up of two components based on an FCN 8 schedule of food reinforcement. In the Fast component, lever presses were spaced by a minimum of 2 s and in the Slow component by a minimum of 5 s. The average chain length was significantly shorter, and the rats were less efficient in the Slow component. Five drugs were tested on this baseline, imipramine (1.0–10.0 mg/kg), ethanol (300–3000 mg/kg administered PO), haloperidol (0.01–0.1 mg/kg), chlordiazepoxide (1.0–10.0 mg/kg) and d-amphetamine (0.2–0.8 mg/kg). All the drugs reduced responding at the highest dose, but imipramine was different from the others in that it increased the average number of responses in the chain and produced a shift in the chain length distribution to the right, possibly reflecting a reduction in impulsivity. The other four drugs reduced chain length at the highest dose, although in the case of ethanol this effect was very small and, unlike the other three drugs, did not result in a shift in the distribution to the left. The paced FCN procedure can differentiate the effects of different drugs on one aspect of impulsivity, and is likely to be a useful procedure for further study of this aspect of behaviour.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002130050674
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  • 8
    Electronic Resource
    Electronic Resource
    The pharmacology of impulsive behaviour in rats II: the effects of amphetamine, haloperidol, imipramine, chlordiazepoxide and other drugs on fixed consecutive number schedules (FCN 8 and FCN 32) (1998)
    Springer
    Psychopharmacology 138 (1998), S. 283-294 
    Details
    ISSN: 1432-2072
    Keywords: Key words Impulsivity ; Amphetamine ; Antidepressant ; Haloperidol ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The effects of drugs on one aspect of impulsive behaviour were evaluated using a schedule in which rats were trained to complete a fixed consecutive number of responses on one of two levers before pressing the second to obtain a reinforcer (FCN). Terminating the chain before completing the FCN resulted in the omission of the food, and can be considered an impulsive decision. Two groups of food-deprived rats were trained to press either 8 or 32 times on the left lever (FCN lever) of a two lever operant chamber before pressing the right lever (Reinforcement lever) to deliver a food pellet. Responding on the Reinforcement lever before completion of the sequence resulted in a short time-out and the rat had to begin the sequence again. After responding had stabilised, the rats were treated with a range of doses of a number of drugs. Impulsivity was assessed by several measures, including the mean chain length and the proportion of chains terminating in food delivery, and the distribution of chain lengths was analysed. The efficiency of the rats was similar under both FCN 8 and FCN 32, although it was more difficult to maintain a consistent baseline under FCN 32. Under the FCN 8 schedule, significant decreases in chain length were obtained with d-amphetamine (0.8–2.4 mg/kg), haloperidol (0.1 mg/kg), ethanol (1 and 3 g/kg) and chlordiazepoxide (10.0 mg/kg), and there were alterations in other measures consistent with an increase in impulsivity. Imipramine (1–10 mg/kg), citalopram (1–10 mg/kg) and metergoline (0.3–3.0 mg/kg) had no effect on mean chain length, although the first two drugs shifted the chain length distribution to the left. d-Amphetamine (0.4–1.2 mg/kg) and PCPA (100 mg/kg) reduced chain length and had other effects consistent with increased impulsivity under FCN 32 schedule, whereas imipramine had little, and citalopram no, effect. Taken generally, effect of the active drugs was relatively non-specific, including both a reduction in response rate and alterations in choice measures proposed to reflect an increase in impulsivity. Detailed analysis of the effect of amphetamine revealed that three processes were at work: chain shortening, an increased preference for the lever most closely associated with food delivery, and a gradual shift in the control over responding from the response sequence (pattern) to the individual lever press (act).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002130050673
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  • 9
    Electronic Resource
    Electronic Resource
    Increased response switching, perseveration and perseverative switching following d-amphetamine in the rat (1983)
    Springer
    Psychopharmacology 80 (1983), S. 67-73 
    Details
    ISSN: 1432-2072
    Keywords: Amphetamine ; Stereotypy ; Locomotor activity ; Switching ; Perseveration ; Attention ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Four experiments examined the effects of d-amphetamine on response switching and perseveration in apparatus allowing a choice of response location. The relative ‘cost’ of a switch between two response locations and repetitive responding at a single location by rats was manipulated in the various test settings to provide baseline probabilities of switching. d-Amphetamine (0.2–2.3 mg/kg) increased response switching. This effect did not depend on switching being necessary to produce reinforcement and was not explained by increases in locomotor activity, motivational change or randomisation of responding. Further evidence was provided in support of a ‘probability-dependency’ hypothesis, that the effect of the drug depends in part upon the baseline probability of a response. A measure of perseveration independent of response switching (extra responses made prior to the collection of food) showed that increased switching and increased perseveration occurred in the same situation at the same doses, although perseveration generally occurred at higher doses than increased switching. Therefore the effect of amphetamine on response switching or repetition depends on the dose of drug, the context of the response and its probability of occurrence under control conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00427498
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  • 10
    Electronic Resource
    Electronic Resource
    Dissociable effects of d-amphetamine, chlordiazepoxide and α-flupenthixol on choice and rate measures of reinforcement in the rat (1983)
    Springer
    Psychopharmacology 79 (1983), S. 180-186 
    Details
    ISSN: 1432-2072
    Keywords: Reinforcement ; Non-reinforcement ; Rate ; Choice ; Win-stay ; d-Amphetamine ; Chlordiazepoxide ; α-Flupenthixol ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The role of reinforcers in influencing choice was studied by use of a schedule that included a random intermixing of reinforced and explicitly non-reinforced components. The just-reinforced response had a high likelihood of being repeated (win-stay), although there was no differential reinforcement for doing so, whereas responses just followed by explicit non-reinforcement had a very low probability of repetition (lose-stay). Non-parametric indices based on the theory of signal detection were used to derive a choice measure of reinforcement which was independent of alterations in average response rate. Treatments with d-amphetamine (0.2–4.5 mg/kg), chlordiazepoxide (0.25–16 mg/kg) and α-flupenthixol (0.03–0.6 mg/kg) showed that changes in the choice measure could be dissociated from changes in the response rate. These findings were supported by extinction and satiation tests.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00427808
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