• Shi-Hong Zhang, Jie Yu, Guo-Dong Lou, Ying-Ying Tang, Ran-Ran Wang, Wei-Wei Hou, and Zhong Chen.
• Department of Pharmacology, Key Laboratory of Medical Neurobiology of the Ministry of Health of China, School of Basic Medical Sciences, Zhejiang University, Hangzhou, China College of Basic Medical Science, Zhejiang Chinese Medical University, Hangzhou, China Department of Pharmacy, Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, Hangzhou, China Department of Pharmacy, Women's Hospital, School of Medicine, Zhejiang University, Hangzhou, China.
• Pain. 2016 Mar 1; 157 (3): 740-749.

AbstractClinical studies show that chronic pain can spread to adjacent or even distant body regions in some patients. However, little is known about how this happens. In this study, we found that partial infraorbital nerve transection (p-IONX) in MRL/MPJ mice induced not only marked and long-lasting orofacial thermal hyperalgesia but also thermal hyperalgesia from day 3 postoperatively (PO) and tactile allodynia from day 7 PO in bilateral hind paws. Pain sensitization in the hind paw was negatively correlated with facial thermal hyperalgesia at early but not late stage after p-IONX. After a rapid activation of c-Fos, excitability and excitatory synaptic neurotransmission in lumbar dorsal horn neurons were elevated from day 3 and day 7 PO, respectively. In addition, microglial activation after p-IONX transmitted caudally from the Vc in the medulla to lumber dorsal horn in a time-dependent manner. Inhibition of microglial activation by minocycline at early but not late stage after p-IONX postponed and attenuated pain sensitization in the hind paw. These results indicate that neuropathic pain after p-IONX in MRL/MPJ mice spreads from the orofacial region to distant somatic regions and that a rostral-caudal transmission of central sensitization in the spinal cord is involved in the spreading process of pain hypersensitivity.

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