Stimulation of the Hippocampal POMC/MC4R Circuit Alleviates Synaptic Plasticity Impairment in an Alzheimer's Disease Model.

Hippocampal synaptic plasticity is modulated by neuropeptides, the disruption of which might contribute to cognitive deficits observed in Alzheimer's disease (AD). Although pro-opiomelanocortin (POMC)-derived neuropeptides and melanocortin 4 receptor (MC4R) are implicated in hippocampus-dependent synaptic plasticity, how the POMC/MC4R system functions in the hippocampus and its role in synaptic dysfunction in AD are largely unknown. Here, we mapped a functional POMC circuit in the mouse hippocampus, wherein POMC neurons in the cornu ammonis 3 (CA3) activate MC4R in the CA1. Suppression of hippocampal MC4R activity in the APP/PS1 transgenic mouse model of AD exacerbates long-term potentiation impairment, which is alleviated by the replenishment of hippocampal POMC/MC4R activity or activation of hippocampal MC4R-coupled Gs signaling. Importantly, MC4R activation rescues amyloid-β-induced synaptic dysfunction via a Gs/cyclic AMP (cAMP)/PKA/cAMP-response element binding protein (CREB)-dependent mechanism. Hence, disruption of this hippocampal POMC/MC4R circuit might contribute to synaptic dysfunction observed in AD, revealing a potential therapeutic target for the disease.