title: Dopamine depletion and subsequent treatment with L-DOPA, but not the long-lived dopamine agonist pergolide, enhances activity of the Akt pathway in the rat striatum.
abstract: Dysregulation of signaling pathways is believed to contribute to Parkinson's disease pathology and l-DOPA-induced motor complications. Long-lived dopamine (DA) agonists are less likely to cause motor complications by virtue of continuous stimulation of DA receptors. In this study, we compared the effects of the unilateral 6-hydroxydopamine lesion and subsequent treatment with l-DOPA and DA agonist pergolide on signaling pathways in rats. Pergolide caused less pronounced behavioral sensitization than l-DOPA (25 mg/kg, i.p., 10 days), particularly at lower dose (0.5 and 0.25 mg/kg, i.p.). Pergolide, but not l-DOPA, reversed lesion-induced up-regulation of preproenkephalin and did not up-regulate preprodynorphine or DA D3 receptor in the lesioned hemisphere. Pergolide was as effective as l-DOPA in reversing the lesion-induced elevation of ERK2 phosphorylation in response to acute apomorphine administration (0.05 mg/kg, s.c.). Chronic l-DOPA significantly elevated the level of Akt phosphorylation at both Thr(308) and Ser(473) and concentration of phosphorylated GSK3alpha, whereas pergolide suppressed the lesion- and/or challenge-induced supersensitive Akt responses. The data indicate that l-DOPA, unlike pergolide, exacerbates imbalances in the Akt pathway caused by the loss of DA. The results support the hypothesis that the Akt pathway is involved in long-term actions of l-DOPA and may be linked to l-DOPA-induced dyskinesia.
authors.affiliation: Department of Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee 37232, USA.
authors.forename: Evgeny
authors.initials: E
authors.lastname: Bychkov
authors.forename: M Rafiuddin
authors.initials: MR
authors.lastname: Ahmed
authors.forename: Kevin N
authors.initials: KN
authors.lastname: Dalby
authors.forename: Eugenia V
authors.initials: EV
authors.lastname: Gurevich
mesh_terms: D000818:Animals; D003342:Corpus Striatum / Q000187:drug effects* / Q000378:metabolism / Q000503:physiopathology; D004298:Dopamine / Q000172:deficiency*; D015259:Dopamine Agents / Q000494:pharmacology; D018491:Dopamine Agonists / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D038362:Glycogen Synthase Kinase 3 / Q000187:drug effects / Q000378:metabolism; D000071679:Glycogen Synthase Kinase 3 beta; D007980:Levodopa / Q000494:pharmacology*; D019950:Mitogen-Activated Protein Kinase 1 / Q000187:drug effects / Q000378:metabolism; D018847:Opioid Peptides / Q000187:drug effects / Q000378:metabolism; D016627:Oxidopamine; D010300:Parkinson Disease / Q000188:drug therapy / Q000378:metabolism / Q000503:physiopathology; D010479:Pergolide / Q000494:pharmacology*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D050637:Receptors, Dopamine D3 / Q000187:drug effects / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects* / Q000502:physiology; D015854:Up-Regulation / Q000187:drug effects / Q000502:physiology
chemical_list: D015259:Dopamine Agents; D018491:Dopamine Agonists; D018847:Opioid Peptides; D050637:Receptors, Dopamine D3; D010479:Pergolide; D007980:Levodopa; D016627:Oxidopamine; D000071679:Glycogen Synthase Kinase 3 beta; D051057:Proto-Oncogene Proteins c-akt; D019950:Mitogen-Activated Protein Kinase 1; D038362:Glycogen Synthase Kinase 3; D004298:Dopamine