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  • 1
    Electronic Resource
    Electronic Resource
    A comparison of the behavioural consequences of chronic stimulation of dopamine receptors in the nucleus accumbens of rat brain effected by a continuous infusion or by single daily injections (1983)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 324 (1983), S. 27-33 
    Details
    ISSN: 1432-1912
    Keywords: Nucleus accumbens ; Dopamine ; Intracerebral injection ; Intracerebral infusion ; Locomotor activity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Mesolimbic dopamine (DA) receptors of the rat were subject to a chronic (13 day) stimulation effected either by single, repeated daily injections or by infusion from osmotic minipumps of 1.56–50 μg DA bilaterally into the nucleus accumbens. Rats were preselected according to their responsiveness to the hyperactivity inducing effect of the DA agonist (−)N-n-propylnorapomorphine [(−)NPA], and the two groups categorised as ‘high’ and ‘low’ activity responders were used in the present studies. Whilst the stimulation of mesolimbic DA receptors by a single acute injection or by a 24 h infusion was ineffective to modify locomotor responding, the repetition of the daily injections or the continuation of the infusion caused dose-related increases in locomotor activity of both groups of rats. The spectrum of enhanced activity responding depended on the mechanism of stimulation, a ‘biphasic’ or ‘monophasic’ pattern resulting from the infusion or daily injections respectively. It was an important observation that a repetitive biting behaviour developed concomitant to the hyperactivity during daily DA injections, a response not observed during infusion, indicating that the nature of the receptor stimulation, continuous or pulsatile, can dictate the development of a motor response. The effects of discontinuing the chronic intra-accumbens stimulation on responsiveness to (−)NPA was the same whether the chronic stimulation was achieved by repeated injection or infusion. However, the consequences of DA withdrawal critically depended on the initial classification of rat activity according to (−)NPA. Thus, initially ‘high’ response animals reversed to ‘high’ responsiveness. Such data may indicate that mesolimbic DA can act to regulate motor performance rather than simply exerting a facilitatory role.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00647834
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Locomotor hyperactivity caused by dopamine infusion into the nucleus accumbens of rat brain: specificity of action (1984)
    Springer
    Psychopharmacology 82 (1984), S. 174-180 
    Details
    ISSN: 1432-2072
    Keywords: Nucleus accumbens ; Intracerebral infusion ; Dopamine ; Neurotransmitter substances ; Locomotor activity ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Rats selected as high-activity and low-activity responders to the hyperactivity-inducing action of peripherally administered (-)N-n-propylnorapomorphine [(-)NPA] were subject to intra-accumbens infusion of dopamine, noradrenaline, serotonin, acetylcholine and GABA (0.48 μl/h, 25 μg/24 h, 13 days). Locomotor activity was measured during infusion and for a minimum of 35 days thereafter. After discontinuation of infusion the animals' responsiveness to (-)NPA was also assessed and, on the 2nd day of withdrawal, sensitivity to the hyperactivity-inducing action of acute intra-accumbens dopamine was determined. Dopamine caused a biphasic pattern of hyperactivity during infusion with peaks of responding between days 2–5 and 8–12: normal values returned after withdrawal of infusion. However, 2–3 weeks after withdrawal of intra-accumbens dopamine infusion animals showed reversed responding to (-)NPA challenge, the initial low-active animals giving a high-active response and high-active animals giving low-activity. Infusions of noradrenaline, serotonin, GABA and acetylcholine produced some increase in locomotor activity towards the termination of infusion, but no treatment could replicate the first hyperactivity peak and no treatment, after withdrawal, could reverse the responsiveness to (-)NPA of high- and low-active animals. Acute injections of dopamine into the nucleus accumbens showed that the infusion of the different neurotransmitter substances caused change within that nucleus. Nevertheless, changes in locomotor behaviour following the infusion of dopamine into the nucleus accumbens are specific for dopamine.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00427768
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Lithium and bupropion antagonise the phasic changes in locomotor activity caused by dopamine infused into the rat nucleus accumbens (1986)
    Springer
    Psychopharmacology 89 (1986), S. 311-316 
    Details
    ISSN: 1432-2072
    Keywords: Nucleus accumbens ; Intracerebral infusion ; Dopamine ; Phasic hyperactivity ; Lithium ; Bupropion ; Antidepressant drugs ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Dopamine infused persistently (25 μg/24 h for 13 days) into the nucleus accumbens of rat brain caused phasic increases in spontaneous locomotor activity during the period of infusion. This phasic responding was prevented by lithium administered throughout the infusion period in divided doses (3×daily administrations of 2.5 mg/kg IP) or as a continuous IP infusion (7.5 mg/kg/24 h), and by bupropion treatment (5–20 mg/kg 3 × daily). In contrast, imipramine, amitriptyline and nomifensine failed to prevent the phasic locomotor response to dopamine at doses which did not by themselves cause marked motor changes. Locomotor activity was measured using individual photocell cages, and rats preselected to (−)NPA were those initially showing a modest locomotor activity. Fourteen to twenty-eight days after discontinuing the dopamine infusion rats showed increased responsiveness to (−)NPA which persisted throughout the remainder of the 70-day withdrawal period. This long-term change was prevented when lithium was given continuously throughout the period of dopamine infusion, but not when lithium was given in divided doses, showing the importance of the mode of drug delivery. The long-term change caused by the dopamine infusion could also be prevented by bupropion but not by imipramine, amitriptyline or nomifensine to show again that the actions of classical antidepressant drugs may be differentiated from those of lithium and bupropion. Therefore, it is suggested that the model of phasic hyperactivity described may provide a means for more closely analysing, both behaviourally and biochemically, the site and mechanism of action of lithium (and bupropion) in the control of the short- and long-term consequences of an enhanced mesolimbic dopamine activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00174366
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    Paper (German National Licenses)
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