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Abstract: Kisspeptin/GPR54 system plays a crucial role in the control of puberty onset and reproductive function. In the present study, we gave the first report that kisspeptin and GPR54 were expressed in the small- to large-sized neurons, and co-localized with Bandeiraea simplicifolia isolectin B4 (IB4), calcitonin-gene-related peptide (CGRP) and neurofilament 200 (NF200) in the L4/5 dorsal root ganglion (DRG) of naïve rats, detected by the double immunofluorescent staining. Interestingly, a marked elevation in the levels of KiSS-1 and GPR54 mRNA as well as protein was observed in the spinal dorsal horn and DRG 4 and 14 days following intra-articular injection of complete Freund''s adjuvant (CFA), indicating a possible involvement of the kisspeptin/GPR54 system in chronic inflammatory pain. [Copyright &y& Elsevier]

Abstract: Electroacupuncture (EA) can effectively control the exaggerated pain in humans with inflammatory disease and animals with experimental inflammatory pain. However, there have been few investigations on the effect of co-administration of EA and analgesics and the underlying synergistic mechanism. Using behavioral test, RT-PCR analysis, enzyme immunoassay (EIA) and enzyme-linked immunosorbent assay (ELISA), the present study demonstrated that (1) Unilateral intra-articular injection of complete Freund''s adjuvant (CFA) produced a constant hyperalgesia and an up-regulation of the prostaglandin E2 (PGE2) level as well as the tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-6 levels in the spinal cord; (2) Celecoxib, a selective inhibitor of cyclooxygenase-2 (COX-2), at a dose of 2, 10, and 20mg/kg (twice daily, p.o.), presented a dose-dependent anti-hyperalgesic effect; (3) Repeated EA stimulation of ipsilateral ‘Huan-Tiao’ (GB30) and ‘Yang-Ling-Quan’ (GB34) acupoints significantly suppressed CFA-induced hyperalgesia, and markedly inhibited the CFA-induced increase of the level of PGE2 as well as IL-1β, IL-6, and TNF-α in the spinal cord; (4) EA combined with low dose of celecoxib (2mg/kg, twice daily, p.o.) greatly enhanced the anti-hyperalgesic effects of EA, with a synergistic reversing effect on CFA-induced up-regulation of spinal PGE2, but not on the IL-1β, IL-6, or TNF-α. These data indicated that repeated EA combined with low dose of celecoxib produced synergistic anti-hyperalgesic effect in the CFA-induced monoarthritic rats, which could be made possible by regulating the activity of spinal COX, hence the spinal PGE2 level. Thus, this combination may provide an effective strategy for pain management. [Copyright &y& Elsevier]

Abstract: Osteomyelitis is an acute or chronic inflammatory process of bone accompanied with mild to severe pain. Generally, mild to moderate pain induced by osteomyelitis can be relieved, yet severe pain cannot. Therefore, a further investigation into the mechanism of severe pain induced by osteomyelitis is needed. In this study, a traditional rat model of osteomyelitis was induced by intra-tibial injection of Staphylococcus aureus. Then, a series of tests including bone histology, blood analysis, mechanical allodynia, thermal hyperalgesia, and immunohistochemistry were performed. Four days after an intra-tibial bacterial injection, acute inflammation was observed in the bone marrow, which developed into chronic inflammation 12 days after the procedure. The results from the blood analysis confirmed the existence of bone inflammation. Significant mechanical allodynia and thermal hyperalgesia developed shortly after the injection. This osteomyelitis-induced pain behavior was reversed by Celecoxib, a selective COX-2 inhibitor. Furthermore, significant increase of both microglia and astrocytes was observed in the spinal cord. Our results suggest that osteomyelitis-induced rats display pain related behaviors and associated neurochemical changes. This study thus provides a novel practical rat model of bone inflammation induced pain. [Copyright &y& Elsevier]

Abstract: In prior studies, models of inflammatory pain were produced through injecting complete Freund''s adjuvant (CFA) or capsaicin directly into either the deep somatic tissue or the animal''s hind paw. In contrast, bone cancer-induced pain (BCIP) was simulated through injecting tumor cells into the cavity of the femur or the tibia. It has been reported that, due to differences in afferent innervation, the same stimulus to various tissue types might result in differing patterns of pain response. Hence, the aim of this study is to establish a rat model of bone inflammation-induced pain (BIIP) by injecting CFA into the tibial cavity, the same site involved in the BCIP model. The differences in body weight, bone histology, mechanical allodynia, thermal hyperalgesia, and the pain relieving effects of Celebrex on this model of BIIP were evaluated. The results showed that there was evidence of significant inflammation seen in the bone marrow two days after intra-tibial CFA injection, including nuclear condensation and fragmentation, massive neutrophilic granulocytes, and prominent fibrinous exudates. Fourteen days after injection, marked fibrosis of the bone was detected by histological staining. After unilateral CFA injection, behavioral studies showed mechanical allodynia to von Frey hair stimulation, but no thermal hyperalgesia was observed. Celebrex showed significant anti-allodynic effects on the BIIP model. The results demonstrated that CFA is an effective agent for inducing bone inflammation and subsequent pain-related behavior in rat models, and, thus, provides a practical and valuable contrast for BCIP research. [Copyright &y& Elsevier]