Imbalance of a serotonergic system in frontotemporal dementia: implication for pharmacotherapy
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Information is sparse on neurotransmitter deficiencies in frontotemporal dementia (FTD), in particular with reference to distinct histological subgroups and Alzheimer’s disease (AD).
To evaluate in FTD with the major histologies, and compare with AD and controls, neurotransmission indices, as these may help in developing treatment.
Materials and methods
Post-mortem grey matter from Brodmann Area 21, 9 and 7 of 51 brains was assayed for ten neurochemical parameters indexing neurotransmission. Repeated measures analyses of variance were carried out for each parameter comparing groups (FTD vs AD vs control) at each anatomical site.
In FTD only the indices of alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid, serotonin (5-HT)1A and 5-HT2A receptors were significantly reduced from control values. Of the ten parameters only 5-HT1A receptors showed significant group × site interaction. This reflected disproportionate reduction in frontal and temporal compared to parietal cortex. In FTD three other receptors (muscarinic, M1, N-methyl-d-aspartate, NMDA, and kainate), choline acetyltransferase (ChAT) activity, 5-HT and 5-hydroxyindoleacetic acid content and 5-HT reuptake site values were not significantly reduced from control values. Only 5-HT, 5-HT reuptake site and ChAT values were significantly higher in FTD than AD. NMDA receptor and ChAT values were significantly reduced from control only in AD.
Neurochemical results in FTD indicate degeneration and loss of pyramidal neurones in frontotemporal neocortex, yet 5-HT afferents and 5-HT concentration, which are inhibitory on pyramidal neurones, were relatively preserved. This could lead to an excess of extraneural 5-HT causing underactivity of surviving pyramidal neurones. Pharmacotherapy with a 5-HT1A receptor antagonist may be indicated.
KeywordsFrontotemporal dementia Neurochemistry Serotonin Serotonin1A receptor
We are grateful to Alan Cross, Anil Misra, Sophie Petit-Zeman, Michelle Qume and Gary Stratman for carrying out some of the assays. Drs S. Afzal, S. Al-Sarraj, Atik Baborie and Bala Doshi and Professors Peter Lantos and Robert Perry kindly helped with the collection and classification of material. DMB is grateful to Oxford University for the award of a McDonnell Visiting Fellowship whilst preparing this manuscript for publication. We also thank Joanna Wilkinson for her help in preparing the manuscript.
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