title: Alzheimer and platelets: low-density platelet populations reveal increased serotonin content in Alzheimer type dementia.
abstract: BACKGROUND
  Alzheimer's disease (AD) is a progressive form of dementia characterized by an increase in the toxic substance β-amyloid in the brain. Platelets display a substantial heterogeneity with respect to density. They further contain a substantial amount of β-amyloid precursor protein. Platelets take up and store serotonin (5-HT) that plays an important role in the pathogenesis of severe depression. The current study aims to investigate platelet serotonin content in different platelet density populations.
  
  
  METHODS
  The study involved 8 patients (age 70±8 (SD) years) (3 females/5 males) with moderate AD. 6 healthy elderly subjects (age 66±9 (SD) years) (3 females/3 males) served as controls. The platelet population was divided into 17 subpopulations according to density, using a linear Percoll™ gradient. Platelets were counted in all fractions. After cell lysis an ELISA technique was employed to determine the 5-HT content in each platelet subfraction.
  
  
  RESULTS
  The two study groups did not differ significantly regarding platelet distribution in the gradients, but AD sufferers have a significantly higher 5-HT content (p<0.05) in the lighter platelet populations.
  
  
  CONCLUSIONS
  AD-type dementia proved to be associated with lighter platelets containing more 5-HT. It is possible that platelets from AD patients release less 5-HT. It is speculated that AD synapses are affected in a manner comparable to platelets, which could explain why 5-HT reuptake inhibitors are less effective in AD dementia.
authors.affiliation: Department of Internal Medicine, Vrinnevi Hospital, Norrköping, Sweden; Department of Social and Welfare, Linköping University, Linköping, Sweden. Electronic address: micha.milovanovic@liu.se.
authors.forename: Micha
authors.initials: M
authors.lastname: Milovanovic
authors.affiliation: Department of Internal Medicine, Vrinnevi Hospital, Norrköping, Sweden.
authors.forename: Kristoffer
authors.initials: K
authors.lastname: Eriksson
authors.affiliation: Department of Neurobiology, Care Sciences and Society (NVS), KI Alzheimer Disease Research Center, Karolinska Institutet, Huddinge, Sweden.
authors.forename: Bengt
authors.initials: B
authors.lastname: Winblad
authors.affiliation: Department of Medical and Health Sciences, Division of Community Medicine/General Practice, Linköping University, Linköping, Sweden.
authors.forename: Staffan
authors.initials: S
authors.lastname: Nilsson
authors.affiliation: Department of Clinical and Experimental Medicine, Linköping University, Linköping, Sweden.
authors.forename: Tomas L
authors.initials: TL
authors.lastname: Lindahl
authors.affiliation: Department of Clinical and Experimental Medicine, Linköping University, Linköping, Sweden.
authors.forename: Claes
authors.initials: C
authors.lastname: Post
authors.affiliation: Department of Internal Medicine, Vrinnevi Hospital, Norrköping, Sweden.
authors.forename: Petter
authors.initials: P
authors.lastname: Järemo
mesh_terms: D000368:Aged; D000544:Alzheimer Disease / Q000097:blood* / Q000473:pathology; D016229:Amyloid beta-Peptides / Q000378:metabolism*; D001792:Blood Platelets / Q000378:metabolism* / Q000473:pathology; D005260:Female; D006801:Humans; D008297:Male; D012701:Serotonin / Q000097:blood*
chemical_list: D016229:Amyloid beta-Peptides; D012701:Serotonin
keywords: Alzheimer's disease; Fibrinogen; Platelet activity; Platelet density; Platelet heterogeneity; Platelets; Serotonin