Neuropathic pain-induced cognitive dysfunction and down-regulation of neuronal pentraxin 2 in the cortex and hippocampus.

Evidence from both basic and clinical science suggests that neuropathic pain can induce cognitive dysfunction. However, these results are mainly based on a series of behavioral tests, there is a lack of quantitative variables to indicate cognitive impairment. Neuronal activity-regulated pentraxin (NPTX2) is a ubiquitously expressed, secreted protein in the nervous system. NPTX2 has been implicated to be involved in a variety of neuropathic diseases including Parkinson's disease, ischemia, and Alzheimer's disease. In a mouse model of chronic pain, NPTX2 is involved in the regulation of inflammatory responses. Here, we employ a variety of behavioral approaches to demonstrate that mice with chronic neuropathic pain have cognitive impairment and exhibit an increased anxiety response. The expression of NPTX2, but not NPTX1, was down-regulated in the hippocampus and cortex after chronic neuropathic pain exposure. The modulation effect of NPTX2 on cognitive function was also verified by behavioral tests using Nptx2 knock-out mice. Above all, we conclude that downregulation of NPTX2 induced by neuropathic pain may serve as an indicator of a progressive cognitive dysfunction during the induction and maintenance of spared nerve injury.