title: Relationship between L-DOPA-induced reduction in motor and exploratory activity and degree of DAT binding in the rat.
abstract: OBJECTIVE
  The present study assessed the influence of L-DOPA administration on neostriatal dopamine (DA) transporter (DAT) binding in relation to motor and exploratory behaviors in the rat.
  
  
  METHODS
  Rats received injections of 5 mg/kg L-DOPA, 10 mg/kg L-DOPA or vehicle. Motor and exploratory behaviors were assessed for 30 min in an open field prior to administration of [(123)I]FP-CIT. Dopamine transporter binding was measured with small animal single-photon emission computed tomography (SPECT) 2 h after radioligand administration for 60 min.
  
  
  RESULTS
  Both L-DOPA doses significantly reduced DAT binding and led to significantly less head-shoulder motility and more sitting relative to vehicle. Moreover, 10 mg/kg L-DOPA induced less distance traveled and ambulation than 5 mg/kg L-DOPA. Analysis of time-behavior (t-b) curves showed that L-DOPA-treated animals relative to vehicle exhibited (1) a faster rate of increase in duration of sitting; (2) a slower rate of increase in duration of head-shoulder motility; and (3) a slower rate of decrease in frequency of head-shoulder motility.
  
  
  CONCLUSIONS
  The reductions of striatal DAT binding after L-DOPA challenges reflected elevated concentrations of synaptic DA. L-DOPA-treated animals showed less head-shoulder motility and more sitting than vehicle-treated animals, indicating an association between less behavioral activity and increased availability of striatal DA. The faster increase of sitting duration to a higher final level and the slower increase of head-shoulder motility to a lower final level relative to controls may be interpreted in terms on behavioral habituation to a novel environment.
authors.affiliation: Clinic of Nuclear Medicine, University Hospital Düsseldorf Düsseldorf, Germany.
authors.forename: Susanne
authors.initials: S
authors.lastname: Nikolaus
authors.affiliation: Clinic of Nuclear Medicine, University Hospital Düsseldorf Düsseldorf, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Beu
authors.affiliation: Center for Behavioural Neuroscience, Institute of Experimental Psychology, Heinrich-Heine University Düsseldorf, Germany.
authors.forename: Angelica Maria
authors.initials: AM
authors.lastname: De Souza Silva
authors.affiliation: Center for Behavioural Neuroscience, Institute of Experimental Psychology, Heinrich-Heine University Düsseldorf, Germany.
authors.forename: Joseph P
authors.initials: JP
authors.lastname: Huston
authors.affiliation: Clinic of Nuclear Medicine, University Hospital Düsseldorf Düsseldorf, Germany.
authors.forename: Hubertus
authors.initials: H
authors.lastname: Hautzel
authors.affiliation: Center for Behavioural Neuroscience, Institute of Experimental Psychology, Heinrich-Heine University Düsseldorf, Germany.
authors.forename: Owen Y
authors.initials: OY
authors.lastname: Chao
authors.affiliation: Clinic of Nuclear Medicine, University Hospital Düsseldorf Düsseldorf, Germany.
authors.forename: Christina
authors.initials: C
authors.lastname: Antke
authors.affiliation: Clinic of Nuclear Medicine, University Hospital Düsseldorf Düsseldorf, Germany.
authors.forename: Hans-Wilhelm
authors.initials: HW
authors.lastname: Müller
keywords: L-DOPA methylester; dopamine transporter; exploratory behavior; habituation; motor behavior; small animal SPECT; time-behavior curves