title: Overexpression of D2/D3 receptors increases efficacy of ropinirole in chronically 6-OHDA-lesioned Parkinsonian rats.
abstract: Ropinirole, which is a non-ergot dopamine agonist derivative, exerts therapeutic benefits in Parkinson's disease (PD). Based on recent studies implicating dopamine receptors 2 and 3 (D2R and D3R) as possible targets of ropinirole, we over-expressed these dopamine receptor genes in the dopamine-denervated striatum of rodents to reveal whether their over-expression modulated ropinirole activity. Adult Sprague-Dawley rats initially received unilateral 6-hydroxydopamine lesion of the medial forebrain bundle. At 1 month after surgery, successfully lesioned animals (3 or less forelimb akinesia score, and 8 or more apomorphine-induced rotations/min over 1 h) were randomly assigned to intrastriatal injection (ipsilateral to the lesion) of blank lentiviral vector, D2R, D3R or both genes. At about 5 months post-lesion, ropinirole (0.2 mg/kg, i.p.) was administered daily for 9 consecutive days. The subtherapeutic dose of ropinirole improved the use of previously akinetic forelimb and produced robust circling behavior in lesioned animals with striatal over-expression of both D2R and D3R compared to lesioned animals that received blank vector. In contrast, the subtherapeutic dose of ropinirole generated only modest motor effects in lesioned animals with sole over-expression of D2R or D3R. Western immunoblot and autoradiographic assays showed enhanced D2R and D3R protein levels coupled with normalized D2R and D3R binding in the ventral striatum of lesioned animals with lentiviral over-expression of both D2R and D3R relative to vehicle-treated lesioned animals. Immunohistochemical analyses showed that D2R and D3R GFP fluorescent cells colocalized with enkephalin and substance P immunoreactive medium spiny neurons. These data support the use of the subtherapeutic dose of ropinirole in a chronic model of PD.
authors.affiliation: Department of Neurology, Medical College of Georgia, Augusta, GA 30912, USA.
authors.forename: N
authors.initials: N
authors.lastname: Matsukawa
authors.forename: M
authors.initials: M
authors.lastname: Maki
authors.forename: T
authors.initials: T
authors.lastname: Yasuhara
authors.forename: K
authors.initials: K
authors.lastname: Hara
authors.forename: G
authors.initials: G
authors.lastname: Yu
authors.forename: L
authors.initials: L
authors.lastname: Xu
authors.forename: K M
authors.initials: KM
authors.lastname: Kim
authors.forename: J C
authors.initials: JC
authors.lastname: Morgan
authors.forename: K D
authors.initials: KD
authors.lastname: Sethi
authors.forename: C V
authors.initials: CV
authors.lastname: Borlongan
mesh_terms: D018663:Adrenergic Agents / Q000009:adverse effects; D000818:Animals; D030801:Animals, Genetically Modified; D000978:Antiparkinson Agents / Q000627:therapeutic use*; D001522:Behavior, Animal / Q000187:drug effects; D004195:Disease Models, Animal; D005552:Forelimb / Q000187:drug effects / Q000503:physiopathology; D005786:Gene Expression Regulation / Q000235:genetics*; D018014:Gene Transfer Techniques; D005822:Genetic Vectors / Q000502:physiology; D007211:Indoles / Q000627:therapeutic use*; D016086:Lentivirus / Q000502:physiology; D008297:Male; D008474:Medial Forebrain Bundle / Q000187:drug effects; D009043:Motor Activity / Q000187:drug effects / Q000502:physiology; D016627:Oxidopamine / Q000009:adverse effects; D010300:Parkinson Disease / Q000188:drug therapy* / Q000209:etiology / Q000378:metabolism / Q000503:physiopathology; D011485:Protein Binding / Q000187:drug effects / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D017448:Receptors, Dopamine D2 / Q000235:genetics / Q000378:metabolism*; D050637:Receptors, Dopamine D3 / Q000235:genetics / Q000378:metabolism*
chemical_list: D018663:Adrenergic Agents; D000978:Antiparkinson Agents; D007211:Indoles; D017448:Receptors, Dopamine D2; D050637:Receptors, Dopamine D3; C046649:ropinirole; D016627:Oxidopamine