Wnt-5a prevents Aβ-induced deficits in long-term potentiation and spatial memory in rats

Although the neurotoxicity of amyloid β (Aβ) protein in Alzheimer's disease (AD) has been reported widely, the exact molecular mechanism underlying the Aβ-induced synaptic dysfunction and memory impairment remains largely unclear. Growing evidence indicates that wingless-type (Wnt) signaling plays an important role in neuronal development, synapse formation and synaptic plasticity. In the present study, we investigated the neuroprotective action of Wnt-5a against the synaptic damage and memory deficit induced by Aβ25-35 by using in vivo electrophysiological recording and Morris water maze (MWM) test. We found that intracerebroventricular (i.c.v.) injection of Aβ25-35 alone did not affect the baseline field excitatory postsynaptic potentials (fEPSPs) and the paired-pulse facilitation (PPF) in the hippocampal CA1 region of rats, but significantly suppressed high frequency stimulation (HFS) induced long-term potentiation (LTP); pretreatment with Wnt-5a prevented the Aβ25-35-induced suppression of hippocampal LTP in a dose-dependent manner; soluble Frizzled-related protein (sFRP), a specific Wnt antagonist, effectively attenuated the protective effects of Wnt-5a. In MWM test, Aβ25-35 alone significantly disrupted spatial learning and memory ability of rats, while pretreatment with Wnt-5a effectively prevented the impairments induced by Aβ25-35. These results in the present study demonstrated for the first time the neuroprotective effects of Wnt-5a against Aβ-induced in vivo synaptic plasticity impairment and memory disorder, suggesting that Wnt signaling pathway is one of the important targets of Aβ neurotoxicity and Wnt-5a might be used as one of the putative candidates for the therapeutic intervention of AD.