title: Rapidly induced dopaminergic supersensitivity: D1/D2 receptor participation and its prevention by an MAO-inhibitor.
abstract: The dopaminergic system requires combined dopamine D1/D2 receptor stimulation to express its activity; a phenomenon called synergism D1/D2. Dopamine receptors develop supersensitivity following dopamine de-afferentation and/or reserpine treatment. Acute supersensitivity occurs with reserpine treatment. The breakdown of D1/D2 synergism has been proposed implicating the genesis of this kind of supersensitivity. We sought to determine the best conditions for inducing acute dopaminergic supersensitivity evaluated by apomorphine-induced stereotyped behaviour, to examine whether D1/D2 synergism breakdown occurs in this reserpine-induced acute supersensitivity model, and whether it can be prevented by the monoamino-oxidase (MAO) inhibitor selegiline. Reserpine (2.0 mg/kg) was injected 3 h before apomorphine (0.6 mg/kg) induced stereotypy. D1/D2 synergism was investigated using specific antagonists (D1-SKF 83566 2.5 mg/kg, D2-haloperidol 2.0 mg/kg) and selegiline (10 mg/kg) was used to analyze the influence of dopamine "de-novo" synthesis. All antagonist treatments suppressed stereotypy and selegiline prevented supersensitivity. These data suggest that reserpine-induced acute dopaminergic supersensitivity is not due to the breakdown of D1/D2 synergism and such supersensitivity can be prevented by recently synthesised dopamine.
authors.affiliation: Department of Physiological Sciences, Medical School of Santa Casa of Sao Paulo, SP., Rua Dr. Cesario Motta Jr. 61, 11 andar, 01221-020, Sao Paulo, SP, Brazil. anakleinman@terra.com.br
authors.forename: Ana
authors.initials: A
authors.lastname: Kleinman
authors.forename: Carla A
authors.initials: CA
authors.lastname: Tieppo
authors.forename: Gabriela M
authors.initials: GM
authors.lastname: Florez
authors.forename: Luciano F
authors.initials: LF
authors.lastname: Felicio
authors.forename: Antonia G
authors.initials: AG
authors.lastname: Nasello
mesh_terms: D000818:Animals; D001058:Apomorphine / Q000494:pharmacology; D008297:Male; D008996:Monoamine Oxidase Inhibitors / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D017447:Receptors, Dopamine D1 / Q000502:physiology*; D017448:Receptors, Dopamine D2 / Q000502:physiology*; D012110:Reserpine / Q000494:pharmacology*; D013239:Stereotyped Behavior / Q000187:drug effects
chemical_list: D008996:Monoamine Oxidase Inhibitors; D017447:Receptors, Dopamine D1; D017448:Receptors, Dopamine D2; D012110:Reserpine; D001058:Apomorphine