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Clin Biochem. 2014 Oct;47(15):51-3. doi: 10.1016/j.clinbiochem.2014.07.007. Epub 2014 Jul 17.

Alzheimer and platelets: low-density platelet populations reveal increased serotonin content in Alzheimer type dementia.

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Department of Internal Medicine, Vrinnevi Hospital, Norrköping, Sweden; Department of Social and Welfare, Linköping University, Linköping, Sweden. Electronic address:
Department of Internal Medicine, Vrinnevi Hospital, Norrköping, Sweden.
Department of Neurobiology, Care Sciences and Society (NVS), KI Alzheimer Disease Research Center, Karolinska Institutet, Huddinge, Sweden.
Department of Medical and Health Sciences, Division of Community Medicine/General Practice, Linköping University, Linköping, Sweden.
Department of Clinical and Experimental Medicine, Linköping University, Linköping, Sweden.



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.


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.


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.


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.


Alzheimer's disease; Fibrinogen; Platelet activity; Platelet density; Platelet heterogeneity; Platelets; Serotonin

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