Deactivation of dorsal CA1 pyramidal neurons projecting to medial prefrontal cortex contributes to neuropathic pain and short-term memory impairment.

Neuropathic pain after peripheral nerve injury is a multidimensional experience that includes sensory, affective, and cognitive components that interact with one another. Hypoexcitation of the medial prefrontal cortex (mPFC) was observed in mice with peripheral nerve injury, but the changes in neural inputs onto the mPFC have not been completely explored. Here, we report that the neural terminals from the dorsal hippocampus CA1 (dCA1) form excitatory connection with layer 5 pyramidal neurons in the prelimbic area (PrL) of the mPFC. Spared nerve injury (SNI) induced a reduction in the intrinsic excitability of dCA1 pyramidal neurons innervating the PrL and impairment in excitatory synaptic transmission onto dCA1 pyramidal cells. Specifically, activating the neural circuit from dCA1 to mPFC alleviated neuropathic pain behaviors and improved novel object recognition ability in SNI mice, whereas deactivating this pathway in naïve animals recapitulated tactile allodynia and memory deficits. These results indicated that hypoactivity in dCA1 pyramidal cells after SNI in turn deactivated layer 5 pyramidal neurons in PrL and ultimately caused pain hypersensitivity and memory deficits.