title: Effects of the adenosine A2A antagonist istradefylline on cognitive performance in rats with a 6-OHDA lesion in prefrontal cortex.
abstract: BACKGROUND
  Altered cognitive function is a common feature of both the early and later stages of Parkinson's disease (PD) that involves alterations in cortical dopamine content. Adenosine A2A antagonists, such as istradefylline, improve motor function in PD, but their effect on cognitive impairment has not been determined.
  
  
  OBJECTIVE
  The present study investigated whether impairment of working memory due to the loss of dopaminergic input into the prefrontal cortex (PFC) is reversed by administration of istradefylline. We also evaluated whether A2A antagonist administration modulates dopamine levels in the PFC.
  
  
  METHODS
  Bilateral lesions of the dopaminergic input to the PFC were produced in rats using 6-hydroxydopamine (6-OHDA). Cognitive performance was evaluated using an object recognition task and delayed alternation task. The effects of istradefylline, donepezil and methamphetamine on cognitive performance were examined. In addition, the effect of istradefylline on extracellular dopamine levels in the PFC was studied.
  
  
  RESULTS
  PFC dopamine levels and cognitive performance were significantly reduced by 6-OHDA lesioning. Istradefylline, donepezil and methamphetamine improved cognitive performance of PFC-lesioned rats. Istradefylline increased dopamine levels in the PFC in both normal and PFC-lesioned rats.
  
  
  CONCLUSIONS
  PFC dopaminergic input plays an important role in working memory performance. Blockade of A2A receptors using istradefylline reverses the changes in cognitive function, and this may be due to an increase in PFC dopamine content. Adenosine A2A receptor antagonists not only improve motor performance in PD but may also lead to improved cognition.
authors.affiliation: Pharmacological Research Laboratories, Research Division, Kyowa Hakko Kirin Co., Ltd, 1188 Shimotogari, Nagaizumi-cho, Sunto-gun, Shizuoka, 411-8731, Japan.
authors.forename: Takako
authors.initials: T
authors.lastname: Kadowaki Horita
authors.forename: Minoru
authors.initials: M
authors.lastname: Kobayashi
authors.forename: Akihisa
authors.initials: A
authors.lastname: Mori
authors.forename: Peter
authors.initials: P
authors.lastname: Jenner
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Kanda
mesh_terms: D058917:Adenosine A2 Receptor Antagonists / Q000494:pharmacology*; D000818:Animals; D003071:Cognition / Q000187:drug effects; D003072:Cognition Disorders / Q000188:drug therapy* / Q000503:physiopathology; D004195:Disease Models, Animal; D000077265:Donepezil; D004298:Dopamine / Q000378:metabolism; D007189:Indans / Q000494:pharmacology; D008297:Male; D008569:Memory Disorders / Q000188:drug therapy / Q000503:physiopathology; D008570:Memory, Short-Term / Q000187:drug effects; D008694:Methamphetamine / Q000494:pharmacology; D016627:Oxidopamine / Q000633:toxicity; D010880:Piperidines / Q000494:pharmacology; D017397:Prefrontal Cortex / Q000187:drug effects* / Q000473:pathology; D011687:Purines / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D058917:Adenosine A2 Receptor Antagonists; D007189:Indans; D010880:Piperidines; D011687:Purines; C111599:istradefylline; D008694:Methamphetamine; D016627:Oxidopamine; D000077265:Donepezil; D004298:Dopamine