Neurophysiological In Vitro Model of Amyloid-β-Induced Deficits of Hippocampal LTP Involving Neuronal Adenosine A_2A...

Amyloid-β peptides (Aβ) are considered a main culprit of Alzheimer's disease (AD), leading to synaptic dysfunction and memory deficits. Although studies in animal models of AD converge to show alterations of synaptic plasticity, namely of long-term potentiation (LTP), the mechanisms through which Aβ affects synaptic function remain to be unveiled. In this study, we established experimental conditions showing that the acute exposure of mouse hippocampal slices to optimized concentrations of Aβ impaired short-term (PPF-paired-pulse facilitation) and long-term (LTP-long-term potentiation) plasticity without altering basal synaptic transmission. We observed that the elimination of extracellular adenosine with adenosine deaminase abrogated the impact of Aβ on synaptic plasticity, showing a mandatory involvement of extracellular adenosine in the neurophysiological effects of Aβ. Additionally, inhibiting adenosine receptor function with caffeine, as well as selectively blocking adenosine A₁ receptors (A₁R) with DPCPX, or adenosine A_2A receptor (A_2AR) with either an antagonist SCH58261 or through knocking out A_2AR, demonstrated that acute Aβ modified mouse hippocampal PPF via A₁R and LTP through A_2AR. Furthermore, the use of slices from mice bearing forebrain-neuron A_2AR deletion, along with the application of α,β-methylene ADP, a CD73 inhibitor, confirmed that the neurophysiological actions of Aβ on hippocampal LTP occur selectively through the overfunction of neuronal A_2AR via CD73-mediated formation of extracellular adenosine. Overall, the exploitation of a neurophysiological model of early AD, based on the acute administration of Aβ to hippocampal slices, confirmed the critical involvement of adenosine signaling in the impact of Aβ on synaptic plasticity.