Cerebral Cortical Glucose Utilization in the Conscious Rat: Evidence for a Circadian Rhythm

Authors

  • P. D. Crane,

    Corresponding author
    1. Research Service, Veterans Administration Medical Center, Brentwood, Los Angeles, California 90073; and Department of Neurology, Reed Neurological Research Center, School of Medicine, University of California, Los Angeles, California 90024, U.S.A.
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  • L. D. Braun,

    1. Research Service, Veterans Administration Medical Center, Brentwood, Los Angeles, California 90073; and Department of Neurology, Reed Neurological Research Center, School of Medicine, University of California, Los Angeles, California 90024, U.S.A.
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  • E. M. Cornford,

    1. Research Service, Veterans Administration Medical Center, Brentwood, Los Angeles, California 90073; and Department of Neurology, Reed Neurological Research Center, School of Medicine, University of California, Los Angeles, California 90024, U.S.A.
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  • A. M. Nyerges,

    1. Research Service, Veterans Administration Medical Center, Brentwood, Los Angeles, California 90073; and Department of Neurology, Reed Neurological Research Center, School of Medicine, University of California, Los Angeles, California 90024, U.S.A.
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  • W. H. Oldendorf

    1. Research Service, Veterans Administration Medical Center, Brentwood, Los Angeles, California 90073; and Department of Neurology, Reed Neurological Research Center, School of Medicine, University of California, Los Angeles, California 90024, U.S.A.
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  • A preliminary account of these results was presented at the 10th Annual Meeting of the American Society for Neurochemistry, Charleston, South Carolina, March 11–16, 1979.

Address reprint requests to Paul D. Crane, Ph.D., Veterans Administration, Brentwood, Bldg. 258, Rm. 331, 11301 Wilshire Blvd., Los Angeles, California 90073.

Abstract

Abstract: The presence of a circadian rhythm of glucose utilization was demonstrated in vivo in rat cerebral cortex. The activity pattern of the rats, living in a controlled lighting regimen with lights on from 7 a.m. to 7 p. m., appeared to coincide with the rate of glucose consumption in the brain. The rate of utilization was measured at 3-h intervals throughout the day and was found to fall from a maximum at 3 a.m. of 0.98 ± 0.13 μmol min−1 g−1 to a minimum of 0.70 ± 0.08 μmol min−1 g−1 at 3 p. m. Brain glucose also varied with time and its fluctuating level weakly correlated with its rate of utilization. Animals entrained on a 5-h (4: 30-9: 30 p. m.) feeding schedule had a similar circadian rhythm, with only a slight increase in amplitude. Reversal of the light cycle caused a disruption in the normal rhythm, but utilization still varied significantly with time of day. The results both indicate the potential error that can be encountered in experiments done at different times of the day and stress the need for awareness of time of day as a factor in measurements of alterations of metabolic rate in the brain.

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