title: Rhes, the Ras homolog enriched in striatum, is reduced under conditions of dopamine supersensitivity.
abstract: Striatal dopamine receptors become supersensitive when dopaminergic input is removed through either surgical denervation or pharmacological depletion. Although alterations such as increased D2 receptor binding and increased receptor-G protein coupling have been described in supersensitive striatal tissue, their roles in the mechanism of supersensitivity remain uncertain. The Ras Homolog Enriched in Striatum (Rhes) is expressed in brain areas that receive dopaminergic input, and here we test whether alterations in its expression accompany treatments that promote dopamine receptor supersensitivity in rats. Removal of dopamine input to the striatum by surgical denervation with 6-hydroxydopamine resulted in a decrease in rhes mRNA expression throughout striatum, as measured with quantitative in situ hybridization. The decrease was detected as early as two weeks and as late as seven months after surgery. Furthermore, a decrease in rhes mRNA was evident after repeated or acute reserpine treatment. Chronic daily injection of rats with the D2 antagonist eticlopride, which is known to up-regulate D2 receptors without inducing profound receptor supersensitivity, did not alter the expression of rhes mRNA in striatum. Thus, changes in rhes mRNA expression are strictly correlated with receptor supersensitivity, perhaps as a result of continuous removal of dopaminergic input. These findings suggest that rhes mRNA expression is maintained by dopamine and may play a role in determining normal dopamine receptor sensitivity.
authors.affiliation: Department of Psychology, University of New Orleans, 2000 Lakeshore Drive, LA 70148, USA. lharriso@uno.edu
authors.forename: L M
authors.initials: LM
authors.lastname: Harrison
authors.forename: G J
authors.initials: GJ
authors.lastname: LaHoste
mesh_terms: D018759:Adrenergic Uptake Inhibitors / Q000494:pharmacology; D000344:Afferent Pathways / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D003342:Corpus Striatum / Q000187:drug effects / Q000378:metabolism*; D003714:Denervation; D004298:Dopamine / Q000172:deficiency*; D018492:Dopamine Antagonists / Q000494:pharmacology; D065127:Dopamine D2 Receptor Antagonists; D015536:Down-Regulation / Q000187:drug effects / Q000502:physiology; D019204:GTP-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology; D008297:Male; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D016627:Oxidopamine; D012333:RNA, Messenger / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D017448:Receptors, Dopamine D2 / Q000378:metabolism*; D012110:Reserpine / Q000494:pharmacology; D013378:Substantia Nigra / Q000378:metabolism / Q000503:physiopathology
chemical_list: D018759:Adrenergic Uptake Inhibitors; D018492:Dopamine Antagonists; D065127:Dopamine D2 Receptor Antagonists; D012333:RNA, Messenger; D017448:Receptors, Dopamine D2; D012110:Reserpine; D016627:Oxidopamine; D019204:GTP-Binding Proteins; C442475:Rasd2 protein, rat; D004298:Dopamine