Table 1.

The effects of apoE isoforms on synaptic integrity and plasticity

Synaptic protein
Synaptophysin Sytaxin1 PSD95	Specific synaptic proteins are altered in the superior temporal cortex of normal aged human brains in an apoE isoform-specific manner (apoE2>apoE3 >apoE4) (130).
Glutamate receptors	Glutamate receptors are decreased in APOE4 carriers of human AD brains (131) and aged female apoE4-TR mice (132).
Dendritic morphology
Dendritic spine density	APOE4 dose inversely correlates with dendritic spine density of DG neurons in both AD patients and aged normal controls (133). ApoE4-TR mice showed age-dependent decrease of spine density in DG and cortex (apoE4<apoE3) (133, 134).
Dendrite complexity	ApoE4-TR mice show progressive dendritic spine deficits with aging (apoE4<apoE3) (135, 136).
EI balance (transmission)
EPSC vs IPSC	Young apoE4-TR mice exhibit deficits in EPSC (apoE4<apoE3) (135, 136), whereas EI balance in aged apoE4-TR mice shows a bias toward inhibition (137).
Synaptic plasticity
LTP	Young apoE4-TR mice exhibit higher LTP strength in the Schaffer collateral pathway of hippocampus (apoE4>apoE3) (98, 138, 139) but lower strength in the perforant pathway than apoE3 (apoE4<apoE3) (140). Under Aβ stress, perforant LTP was severely impaired in apoE4 mice compared with apoE2-TR mice (141).
LTD	Unknown

Abbreviations: DG, dental gyrus; EPSC, excitatory postsynaptic potential; IPSC, inhibitory postsynaptic potential; LTP, long-term potentiation; LTD, long-term depression; Aβ, amyloid-β.