Chronic Administration of Lithium or Other Antidepressants Increases Levels of DARPP-32 in Rat Frontal Cortex |
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Authors: | Xavier Guitart Eric J. Nestler |
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Affiliation: | Laboratory of Molecular Psychiatry, Departments of Psychiatry and Pharmacology, Yale University School of Medicine, Connecticut Mental Health Center, New Haven, Connecticut, U.S.A. |
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Abstract: | Abstract: We studied the chronic actions of lithium on rat brain by investigating its effects on cyclic AMP-dependent protein phos-phorylation by use of a back-phosphorylation procedure. We identified one heavily regulated phosphoprotein in frontal cortex as the 32-kDa dopamine- and cyclic AMP-regulated phosphoprotein (DARPP-32). Immunoblot experiments demonstrated that chronic lithium regulation of DARPP-32 back-phosphorylation is associated with equivalent increases in levels of DARPP-32 immunoreactivity. Lithium regulation of DARPP-32 immunoreactivity required chronic drug administration and was not observed in several other brain regions examined. Moreover, chronic administration of the antidepressant imipramine or tranylcypromine produced a similar increase in levels of DARPP-32 in frontal cortex, whereas other types of psychotropic drugs, including haloperidol. morphine, and cocaine, did not influence DARPP-32 levels. Increased levels of DARPP-32 could reflect a common functional effect on frontal cortex of long-term exposure to lithium and some other antidepressant medications, an effect possibly related to the clinical actions of these drugs. |
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Keywords: | Lithium Imipramine Tranylcypromine Cyclic AMP-dependent protein phosphorylation |
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