Curve-shift analysis of self-stimulation in food-restricted rats: relationship between daily meal, plasma corticosterone and reward sensitization

Curve-shift analysis of self-stimulation in food-restricted rats: relationship between daily... Chronic food restriction lowers the threshold for lateral hypothalamic electrical self-stimulation (LHSS). This effect has previously been interpreted to reflect a sensitization of reward. In the present study a curve-shift method was used to explicitly differentiate effects of food restriction on brain stimulation rewarding efficacy and performance. Food restriction consistently shifted rate-frequency curves to the left, lowering the M-50 and Theta-0 parameters of rewarding efficacy. Asymptotic rates of reinforcement and slopes of rate-frequency functions were unaffected, confirming that food restriction does not facilitate LHSS by enhancing performance. In this and previous studies, LHSS in food-restricted rats was measured in the period immediately preceding the daily meal when hunger (i.e., period since last meal) and plasma corticosterone are at peak levels. In the light of evidence that corticosterone may regulate sensitivity of the mesolimbic dopamine pathway and account for the sensitizing effect of stress on psychomotor effects of opiates and stimulants, LHSS and corticosterone were measured in the immediate pre-and post-meal periods. While all food-restricted rats displayed elevated corticosterone levels in the pre-meal period and generally displayed a decline to control levels in the post-meal period, the sensitization of reward was not reversed in the post-meal period. These results indicate that chronic food restriction produces a sensitization of reward that does not depend upon the acute state of hunger that precedes the daily meal and does not vary with dynamic changes in plasma corticosterone level. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Brain Research Elsevier

Curve-shift analysis of self-stimulation in food-restricted rats: relationship between daily meal, plasma corticosterone and reward sensitization

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Publisher
Elsevier
Copyright
Copyright © 1995 Elsevier Science B.V. All rights reserved
ISSN
0006-8993
DOI
10.1016/0006-8993(95)00764-H
Publisher site
See Article on Publisher Site

Abstract

Chronic food restriction lowers the threshold for lateral hypothalamic electrical self-stimulation (LHSS). This effect has previously been interpreted to reflect a sensitization of reward. In the present study a curve-shift method was used to explicitly differentiate effects of food restriction on brain stimulation rewarding efficacy and performance. Food restriction consistently shifted rate-frequency curves to the left, lowering the M-50 and Theta-0 parameters of rewarding efficacy. Asymptotic rates of reinforcement and slopes of rate-frequency functions were unaffected, confirming that food restriction does not facilitate LHSS by enhancing performance. In this and previous studies, LHSS in food-restricted rats was measured in the period immediately preceding the daily meal when hunger (i.e., period since last meal) and plasma corticosterone are at peak levels. In the light of evidence that corticosterone may regulate sensitivity of the mesolimbic dopamine pathway and account for the sensitizing effect of stress on psychomotor effects of opiates and stimulants, LHSS and corticosterone were measured in the immediate pre-and post-meal periods. While all food-restricted rats displayed elevated corticosterone levels in the pre-meal period and generally displayed a decline to control levels in the post-meal period, the sensitization of reward was not reversed in the post-meal period. These results indicate that chronic food restriction produces a sensitization of reward that does not depend upon the acute state of hunger that precedes the daily meal and does not vary with dynamic changes in plasma corticosterone level.

Journal

Brain ResearchElsevier

Published: Oct 16, 1995

References

  • Feeding-associated corticosterone peak in rats under various feeding cycles
    Honma, K.I.; Honma, S.; Hiroshige, T.
  • Control of neuronal excitability by corticosteroid hormones
    Joels, M.; de Kloet, E.R.
  • The effects of opioid peptides on dopamine release in the nucleus accumbens: an in vivo microdialysis study
    Spanagel, R.; Herz, A.; Shippenberg, T.S.

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