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[Activation of microglia and astrocytes in different spinal segments after peripheral nerve injury in mice.] [Article in Chinese]

Liu Nian, ZANG Kai-Kai, ZHANG Yu-Qiu^*

Institute of Neurobiology, Fudan University, Shanghai 200032, China

Abstract

Spinal microglia and astrocytes play an important role in mediating behavioral hypersensitive state following peripheral nerve injury. However, little is known about the expression patterns of activated microglia and astrocytes in the spinal dorsal horn. The aim of the present study was to investigate the spatial distribution of microglial and astrocytic activation in cervical, thoracic, lumbar and sacral segments of spinal dorsal horn following chronic constriction injury (CCI) of sciatic nerve. The hind paw withdrawal threshold (PWT) of wild type (WT), CX3CR1YFP and GFAPYFP transgenic mice to mechanical stimulation was determined by von Frey test. Immunofluorescence staining was used to examine the spatial distribution of microglial and astrocytic activation in the spinal dorsal horn. Following CCI, all the WT, CX3CR1YFP and GFAPYFP mice developed robust allodynia in the ipsilateral paw on day 3 after CCI, and the allodynia was observed to last for 14 days. In comparison with sham groups, the PWTs of CCI group animals were significantly decreased (P < 0.01, n = 6). On day 14 after CCI, CX3CR1YFP-GFP immunofluorescence intensity was significantly increased in the ipsilateral lumbar spinal dorsal horn of the CX3CR1YFP mice (P < 0.01, n = 6), but no detectable changes were observed in other spinal segments. Increased GFAPYFP-GFP immunofluorescence intensity was observed in the ipsilateral thoracic, lumbar and sacral spinal segments of the GFAPYFP mice on day 14 after CCI. Iba-1 and GFAP immunofluorescence staining in WT mice showed the same result of microglia and astrocyte activation on day 14 after CCI. CX3CR1YFP-GFP and GFAPYFP-GFP immunofluorescence signal was colocalized with microglial marker Iba-1 and astrocytic marker GFAP, respectively. Interestingly, on day 3 after CCI, Iba-1-immunoreactivity was significantly increased in the ipsilateral thoracic, lumbar and sacral spinal segments of WT mice, whereas the significant upregulation of GFAP-immunoreactivity restrictedly occurred in the ipsilateral lumbar spinal segment. These results suggest that microglial and astrocytic activation may be involved in the development and maintenance of secondary allodynia in mice with neuropathic pain.

Key words: microglia; astrocytes; chronic constriction injury; spinal dorsal horn

Received: 2015-06-10　　Accepted: 2015-08-06

Corresponding author: 张玉秋　　E-mail: yuqiuzhang@fudan.edu.cn

Citing This Article：

Liu Nian, ZANG Kai-Kai, ZHANG Yu-Qiu. [Activation of microglia and astrocytes in different spinal segments after peripheral nerve injury in mice.] [Article in Chinese]. Acta Physiol Sin 2015; 67 (6): 571-582 (in Chinese with English abstract).