Regulation of μ-Opioid Receptor mRNA in Rat Globus Pallidus: Effects of Enkephalin Increases Induced by Short- and Long-Term Haloperidol Administration

Authors

  • Jill M. Delfs,

    1. Department of Pharmacology and Institute of Neurological Sciences, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania;
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  • Lei Yu,

    1. Department of Medical and Molecular Genetics, Indiana University School of Medicine, Indianapolis, Indiana; and
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  • Gaylord D. Ellison,

    1. Department of Psychology, University of California, Los Angeles, California, U.S.A.
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  • Terry Reisine,

    1. Department of Pharmacology and Institute of Neurological Sciences, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania;
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  • Marie-Françoise Chesselet

    Corresponding author
    1. Department of Pharmacology and Institute of Neurological Sciences, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania;
      Address correspondence and reprint requests to Dr. M.-F. Chesselet at Department of Pharmacology, University of Pennsylvania Medical School, 36th Street & Hamilton Walk, Philadelphia, PA 19104, U.S.A.
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Address correspondence and reprint requests to Dr. M.-F. Chesselet at Department of Pharmacology, University of Pennsylvania Medical School, 36th Street & Hamilton Walk, Philadelphia, PA 19104, U.S.A.

Abstract

Abstract: The mRNA encoding μ-opioid receptors is expressed in neurons of the globus pallidus, a region of the basal ganglia that receives a dense enkephalinergic innervation from the striatum. The regulation of the mRNAs encoding the opioid peptide enkephalin in the striatum and the μ-opioid receptor in the globus pallidus was examined with in situ hybridization histochemistry following short- or long-term haloperidol treatments, which alter striatal enkephalin mRNA levels. Animals were administered haloperidol daily for 3 or 7 days (1 mg/kg, s.c.) or continuously for 8 months (1 mg/kg, depot followed by oral). Enkephalin and μ-opioid receptor mRNA levels were unchanged after 3 days of haloperidol treatment. In contrast, the enkephalin mRNA level was increased in the striatum, and μ-opioid receptor mRNA levels were markedly decreased in the globus pallidus after 7 days of haloperidol administration. Similar effects were observed in rats treated with haloperidol for 8 months. The results provide the first evidence of regulation of μ-opioid receptor mRNA in vivo.

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