title: GABA(A) receptor-mediated acceleration of aging-associated memory decline in APP/PS1 mice and its pharmacological treatment by picrotoxin.
abstract: Advanced age and mutations in the genes encoding amyloid precursor protein (APP) and presenilin (PS1) are two serious risk factors for Alzheimer's disease (AD). Finding common pathogenic changes originating from these risks may lead to a new therapeutic strategy. We observed a decline in memory performance and reduction in hippocampal long-term potentiation (LTP) in both mature adult (9-15 months) transgenic APP/PS1 mice and old (19-25 months) non-transgenic (nonTg) mice. By contrast, in the presence of bicuculline, a GABA(A) receptor antagonist, LTP in adult APP/PS1 mice and old nonTg mice was larger than that in adult nonTg mice. The increased LTP levels in bicuculline-treated slices suggested that GABA(A) receptor-mediated inhibition in adult APP/PS1 and old nonTg mice was upregulated. Assuming that enhanced inhibition of LTP mediates memory decline in APP/PS1 mice, we rescued memory deficits in adult APP/PS1 mice by treating them with another GABA(A) receptor antagonist, picrotoxin (PTX), at a non-epileptic dose for 10 days. Among the saline vehicle-treated groups, substantially higher levels of synaptic proteins such as GABA(A) receptor alpha1 subunit, PSD95, and NR2B were observed in APP/PS1 mice than in nonTg control mice. This difference was insignificant among PTX-treated groups, suggesting that memory decline in APP/PS1 mice may result from changes in synaptic protein levels through homeostatic mechanisms. Several independent studies reported previously in aged rodents both an increased level of GABA(A) receptor alpha1 subunit and improvement of cognitive functions by long term GABA(A) receptor antagonist treatment. Therefore, reduced LTP linked to enhanced GABA(A) receptor-mediated inhibition may be triggered by aging and may be accelerated by familial AD-linked gene products like Abeta and mutant PS1, leading to cognitive decline that is pharmacologically treatable at least at this stage of disease progression in mice.
authors: Laboratory for Alzheimer's Disease, RIKEN Brain Science Institute, Wako-shi, Saitama, Japan.
authors: Yuji
authors: Y
authors: Yoshiike
authors: Tetsuya
authors: T
authors: Kimura
authors: Shunji
authors: S
authors: Yamashita
authors: Hiroyuki
authors: H
authors: Furudate
authors: Tatsuya
authors: T
authors: Mizoroki
authors: Miyuki
authors: M
authors: Murayama
authors: Akihiko
authors: A
authors: Takashima
mesh_terms: D000375:Aging / Q000502:physiology*; D016564:Amyloid beta-Protein Precursor / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D003072:Cognition Disorders / Q000503:physiopathology / Q000517:prevention & control; D018756:GABA Antagonists / Q000627:therapeutic use*; D006801:Humans; D007858:Learning / Q000187:drug effects / Q000502:physiology; D017774:Long-Term Potentiation / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D018782:Maze Learning / Q000187:drug effects; D008569:Memory Disorders / Q000503:physiopathology* / Q000517:prevention & control*; D051379:Mice; D008822:Mice, Transgenic; D010852:Picrotoxin / Q000627:therapeutic use*; D053764:Presenilin-1 / Q000187:drug effects / Q000378:metabolism*; D011963:Receptors, GABA-A / Q000187:drug effects / Q000502:physiology*
chemical_list: D016564:Amyloid beta-Protein Precursor; D018756:GABA Antagonists; D010852:Picrotoxin; D053764:Presenilin-1; D011963:Receptors, GABA-A