title: Alterations in NMDA receptor subunit densities and ligand binding to glycine recognition sites are associated with chronic anxiety in Alzheimer's disease.
abstract: Glutamatergic deficits are established neuropathological features of Alzheimer's disease (AD) and are known to correlate with cognitive impairments. In contrast, the role of glutamatergic alterations in behavioral and psychological symptoms of dementia (BPSD) is unclear. There is considerable preclinical evidence for the importance of glycine recognition sites (GlyRS) of N-methyl-D-aspartate (NMDA) receptors in the regulation of anxiety behaviors. This study aimed to correlate several glutamatergic measures with chronic anxiety in AD. Twenty-one AD patients assessed by the Neuropsychiatric Inventory (NPI) were divided into low anxiety (LA) and high anxiety (HA) subgroups. GlyRS and NMDA channel were measured by brain homogenate binding with [(3)H]MDL105,519 and [(3)H]MK-801, respectively. Densities of NMDA receptor NR2A, NR2B and alternate spliced NR1 subunits were quantified by immunoblotting. We found that the binding affinity to GlyRS was significantly higher in HA compared to LA, and this higher GlyRS affinity correlated with selective reduction of NR2A density as well as with elevated anxiety scores. Our observations suggest a novel mechanism whereby subunit specific changes in the NMDA receptor complex may be linked to chronic anxiety in AD via effects on GlyRS function. We propose that NR2A and GlyRS should be further assessed as novel targets of behavioral pharmacotherapy in AD.
authors: Dementia Research Laboratory, Department of Clinical Research, Singapore General Hospital, Singapore.
authors: Shirley W Y
authors: SW
authors: Tsang
authors: Harry V
authors: HV
authors: Vinters
authors: Jeffrey L
authors: JL
authors: Cummings
authors: Peter T-H
authors: PT
authors: Wong
authors: Christopher P L-H
authors: CP
authors: Chen
authors: Mitchell K P
authors: MK
authors: Lai
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000150:complications / Q000378:metabolism* / Q000503:physiopathology; D001008:Anxiety Disorders / Q000175:diagnosis / Q000378:metabolism* / Q000503:physiopathology; D001667:Binding, Competitive / Q000502:physiology; D001921:Brain / Q000378:metabolism* / Q000503:physiopathology; D002908:Chronic Disease; D005260:Female; D018698:Glutamic Acid / Q000378:metabolism*; D005998:Glycine / Q000378:metabolism; D006801:Humans; D008024:Ligands; D008297:Male; D019579:Neocortex / Q000378:metabolism; D009474:Neurons / Q000378:metabolism; D009483:Neuropsychological Tests; D011485:Protein Binding / Q000502:physiology; D021122:Protein Subunits / Q000378:metabolism; D011869:Radioligand Assay; D018009:Receptors, Glycine / Q000378:metabolism*; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism*
chemical_list: D008024:Ligands; C120997:NR2A NMDA receptor; D021122:Protein Subunits; D018009:Receptors, Glycine; D016194:Receptors, N-Methyl-D-Aspartate; D018698:Glutamic Acid; D005998:Glycine