title: Guanfacine produces differential effects in frontal cortex compared with striatum: assessed by phMRI BOLD contrast.
abstract: BACKGROUND
  Guanfacine (an alpha-(2A) adrenoreceptor agonist) is a drug of benefit in the treatment of attention deficit hyperactivity disorder (ADHD) (Taylor FB, Russo J, J Clin Psychopharmacol 21:223-228, 2001). Assessment of this drug using neuroimaging will provide information about the brain regions involved in its effects.
  
  
  OBJECTIVE
  The pharmacological magnetic resonance imaging blood oxygenation level dependent (BOLD) response was determined in rat brain regions following administration of guanfacine.
  
  
  METHODS
  Male rats were individually placed into a 2.35 T Bruker magnet for 60 min to achieve basal recording of changes in signal intensity. Either saline (n = 9) or guanfacine (0.3 mg/kg, i.p.; n = 9) was then administered and recording was continued for a further 90 min. Data were analysed for BOLD effects using statistical parametric maps. Respiration rate, blood pressure and blood gases were monitored and remained constant throughout scanning.
  
  
  RESULTS
  The main changes observed were negative BOLD effects in the caudate putamen and nucleus accumbens with positive BOLD effects in frontal association, prelimbic and motor cortex areas.
  
  
  CONCLUSIONS
  These data suggest that guanfacine can decrease neuronal activity in the caudate while increasing frontal cortex activity. This ability to change neuronal activity in specific areas of rat brain that are known to be impaired in ADHD (Solanto MV, Behav Brain Res 130:65-71, 2002) may contribute to guanfacine's beneficial effects.
authors.affiliation: School of Biomedical Sciences, Medical School, Institute of Neuroscience, University of Nottingham, Queens Medical Centre, Nottingham, NG7 2UH, UK. neil.easton@nottingham.ac.uk
authors.forename: Neil
authors.initials: N
authors.lastname: Easton
authors.forename: Yasmene B
authors.initials: YB
authors.lastname: Shah
authors.forename: Fiona H
authors.initials: FH
authors.lastname: Marshall
authors.forename: Kevin C
authors.initials: KC
authors.lastname: Fone
authors.forename: Charles A
authors.initials: CA
authors.lastname: Marsden
mesh_terms: D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000818:Animals; D003342:Corpus Striatum / Q000187:drug effects* / Q000502:physiology; D005625:Frontal Lobe / Q000187:drug effects* / Q000502:physiology; D016316:Guanfacine / Q000494:pharmacology*; D008279:Magnetic Resonance Imaging; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D000316:Adrenergic alpha-Agonists; D016316:Guanfacine