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  • 1
    ISSN: 1432-2072
    Keywords: Self-injection ; Self-administration ; Amphetamine ; Nucleus accumbens ; Rats
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Rats learned to self-administer d-amphetamine (10 μg/μl) through a cannula implanted in the nucleus accumbens. They responded more frequently for 65±15 nl of amphetamine than for equal amounts of saline. When presented with two levers (one amphetamine, one blank) they responded more on the correct lever for amphetamine. They would also switch levers, when necessary, to maintain access to the drug. When half the usual drug intake was given automatically, animals reduced their response rate by half, thus self-regulating the total amount of amphetamine they received. In tests for leakage into the ventricles, eight rats that self-injected with an accumbens cannula showed response extinction when switched to a ventricular cannula. We conclude that amphetamine self-injected into the accumbens is a positive reinforcer. This localization of ‘amphetamine reward’ suggests that the nucleus accumbens contains a synaptic mechanism underlying amphetamine abuse and, perhaps, also natural reinforcement of behavior.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-2072
    Keywords: Feeding ; Obesity ; 6-Hydroxydopamine ; Amphetamine ; Fenfluramine ; Anorexia ; Catecholamines
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Rats were made hyperphagic by 6-hydroxydopamine (6-OHDA) injected bilaterally into the ventral midbrain; then they were restricted to a 6h/day feeding schedule and tested for appetite suppression with amphetamine and fenfluramine in randomized order. Amphetamine anorexia was diminished while fenfluramine anorexia was enhanced (both P〈0.001). The opposite effect on fenfluramine anorexia shows that the effect of 6-OHDA on amphetamine anorexia was not due to hyperphagia masking the anorexia. Norepinephrine in the forebrain was 90% depleted, but DA and serotonin levels were within 9% of normal. These results demonstrate a new way to dissociate amphetamine and fenfluramine anorexia, as others have done with lateral hypothalamic lesions or DA depletion. The 6-OHDA injections, which were of a type that cause hyperphagia, apparently destroyed a substrate for amphetamine anorexia and also facilitated a substrate for fenfluramine anorexia.
    Type of Medium: Electronic Resource
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