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Liu N, Zang KK, Zhang YQ. [Activation of microglia and astrocytes in different spinal segments after peripheral nerve injury in mice]. Sheng Li Xue Bao 2015; 67:571-582. [PMID: 26701632] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
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), CX3CR1(YFP) and GFAP(YFP) 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, CX3CR1(YFP) and GFAP(YFP) 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, CX3CR1(YFP)-GFP immunofluorescence intensity was significantly increased in the ipsilateral lumbar spinal dorsal horn of the CX3CR1(YFP) mice (P < 0.01, n = 6), but no detectable changes were observed in other spinal segments. Increased GFAP(YFP)-GFP immunofluorescence intensity was observed in the ipsilateral thoracic, lumbar and sacral spinal segments of the GFAP(YFP) 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. CX3CR1(YFP)-GFP and GFAP(YFP)-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.
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Affiliation(s)
- Nian Liu
- Institute of Neurobiology, Fudan University, Shanghai 200032, China
| | - Kai-Kai Zang
- Institute of Neurobiology, Fudan University, Shanghai 200032, China
| | - Yu-Qiu Zhang
- Institute of Neurobiology, Fudan University, Shanghai 200032, China.
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Gu XY, Liu BL, Zang KK, Yang L, Xu H, Pan HL, Zhao ZQ, Zhang YQ. Dexmedetomidine inhibits Tetrodotoxin-resistant Nav1.8 sodium channel activity through Gi/o-dependent pathway in rat dorsal root ganglion neurons. Mol Brain 2015; 8:15. [PMID: 25761941 PMCID: PMC4350947 DOI: 10.1186/s13041-015-0105-2] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2014] [Accepted: 02/18/2015] [Indexed: 11/12/2022] Open
Abstract
Background Systemically administered dexmedetomidine (DEX), a selective α2 adrenergic receptor (α2-AR) agonists, produces analgesia and sedation. Peripherally restricted α2-AR antagonist could block the analgesic effect of systemic DEX on neuropathic pain, with no effect on sedation, indicating peripheral analgesic effect of DEX. Tetrodotoxin-resistant (TTX-R) sodium channel Nav1.8 play important roles in the conduction of nociceptive sensation. Both α2-AR and Nav1.8 are found in small nociceptive DRG neurons. We, therefore, investigated the effects of DEX on the Nav1.8 currents in acutely dissociated small-diameter DRG neurons. Results Whole-cell patch-clamp recordings demonstrated that DEX concentration-dependently suppressed TTX-R Nav1.8 currents in small-diameter lumbar DRG neurons. DEX also shifted the steady-state inactivation curves of Nav1.8 in a hyperpolarizing direction and increased the threshold of action potential and decrease electrical and chemical stimuli-evoked firings in small-diameter DRG neurons. The α2-AR antagonist yohimbine or α2A-AR antagonist BRL44408 but not α2B-AR antagonist imiloxan blocked the inhibition of Nav1.8 currents by DEX. Immunohistochemistry results showed that Nav1.8 was predominantly expressed in peripherin-positive small-diameter DRG neurons, and some of them were α2A-AR-positive ones. Our electrophysiological recordings also demonstrated that DEX-induced inhibition of Nav1.8 currents was prevented by intracellular application of G-protein inhibitor GDPβ-s or Gi/o proteins inhibitor pertussis toxin (PTX), and bath application of adenylate cyclase (AC) activator forskolin or membrane-permeable cAMP analogue 8-Bromo-cAMP (8-Br-cAMP). PKA inhibitor Rp-cAMP could mimic DEX-induced inhibition of Nav1.8 currents. Conclusions We established a functional link between α2-AR and Nav1.8 in primary sensory neurons utilizing the Gi/o/AC/cAMP/PKA pathway, which probably mediating peripheral analgesia of DEX.
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Affiliation(s)
- Xi-Yao Gu
- Institute of Neurobiology, Institutes of Brain Science and State Key Laboratory of Medical Neurobiology, Collaborative Innovation Center for Brain Science, Fudan University, 138 Yi Xue Yuan Road, Shanghai, 200032, China.
| | - Ben-Long Liu
- Institute of Neurobiology, Institutes of Brain Science and State Key Laboratory of Medical Neurobiology, Collaborative Innovation Center for Brain Science, Fudan University, 138 Yi Xue Yuan Road, Shanghai, 200032, China.
| | - Kai-Kai Zang
- Institute of Neurobiology, Institutes of Brain Science and State Key Laboratory of Medical Neurobiology, Collaborative Innovation Center for Brain Science, Fudan University, 138 Yi Xue Yuan Road, Shanghai, 200032, China.
| | - Liu Yang
- Institute of Neurobiology, Institutes of Brain Science and State Key Laboratory of Medical Neurobiology, Collaborative Innovation Center for Brain Science, Fudan University, 138 Yi Xue Yuan Road, Shanghai, 200032, China.
| | - Hua Xu
- Department of Anesthesiology, Changhai Hospital, The Second Military Medical University, Shanghai, 200433, China.
| | - Hai-Li Pan
- Center for Neuropsychiatric Diseases, Institute of Life Science, Nanchang University, Nanchang, 330031, China.
| | - Zhi-Qi Zhao
- Institute of Neurobiology, Institutes of Brain Science and State Key Laboratory of Medical Neurobiology, Collaborative Innovation Center for Brain Science, Fudan University, 138 Yi Xue Yuan Road, Shanghai, 200032, China.
| | - Yu-Qiu Zhang
- Institute of Neurobiology, Institutes of Brain Science and State Key Laboratory of Medical Neurobiology, Collaborative Innovation Center for Brain Science, Fudan University, 138 Yi Xue Yuan Road, Shanghai, 200032, China.
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Cao H, Zang KK, Han M, Zhao ZQ, Wu GC, Zhang YQ. Inhibition of p38 mitogen-activated protein kinase activation in the rostral anterior cingulate cortex attenuates pain-related negative emotion in rats. Brain Res Bull 2014; 107:79-88. [PMID: 25038392 DOI: 10.1016/j.brainresbull.2014.06.005] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2014] [Revised: 06/19/2014] [Accepted: 06/25/2014] [Indexed: 01/12/2023]
Abstract
The emotional components of pain are far less studied than the sensory components. Previous studies have indicated that the rostral anterior cingulate cortex (rACC) is implicated in the affective response to noxious stimuli. Activation of p38 mitogen-activated protein kinase (MAPK) in the spinal cord has been documented to play an important role in diverse kinds of pathological pain states. We used formalin-induced conditioned place aversion (F-CPA) in rats, an animal model believed to reflect the emotional response to pain, to investigate the involvement of p38 MAPK in the rACC after the induction of affective pain. Intraplantar formalin injection produced a significant activation of p38 MAPK, as well as mitogen-activated kinase kinase (MKK) 3 and MKK6, its upstream activators, in the bilateral rACC. p38 MAPK was elevated in both NeuN-positive neurons and Iba1-positive microglia in the rACC, but not GFAP-positive cells. Blocking p38 MAPK activation in the bilateral rACC using its specific inhibitor SB203580 or SB239063 dose-dependently suppressed the formation of F-CPA. Inhibiting p38 MAPK activation did not affect formalin-induced two-phase spontaneous nociceptive response and low intensity electric foot-shock induced CPA. The present study demonstrated that p38 MAPK signaling pathway in the rACC contributes to pain-related negative emotion. Thus, a new pharmacological strategy targeted at the p38 MAPK cascade may be useful in treating pain-related emotional disorders.
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Affiliation(s)
- Hong Cao
- Institute of Neurobiology, Institute of Brain Science and State Key Laboratory of Medical Neurobiology, Shanghai Medical College, Fudan University, Shanghai 200032, China.
| | - Kai-Kai Zang
- Institute of Neurobiology, Institute of Brain Science and State Key Laboratory of Medical Neurobiology, Shanghai Medical College, Fudan University, Shanghai 200032, China
| | - Mei Han
- Institute of Neurobiology, Institute of Brain Science and State Key Laboratory of Medical Neurobiology, Shanghai Medical College, Fudan University, Shanghai 200032, China
| | - Zhi-Qi Zhao
- Institute of Neurobiology, Institute of Brain Science and State Key Laboratory of Medical Neurobiology, Shanghai Medical College, Fudan University, Shanghai 200032, China
| | - Gen-Cheng Wu
- Department of Integrative Medicine and Neurobiology, Institutes of Brain Research, State Key Laboratory of Medical Neurobiology, Fudan University, Shanghai 200032, China
| | - Yu-Qiu Zhang
- Institute of Neurobiology, Institute of Brain Science and State Key Laboratory of Medical Neurobiology, Shanghai Medical College, Fudan University, Shanghai 200032, China
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