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Papers of the Week


Papers: 15 Feb 2020 - 21 Feb 2020


Animal Studies


2020 Feb 14


Pain

Peripheral and central nervous system alterations in a rat model of inflammatory arthritis.

Authors

Locke S, Yousefpour N, Mannarino M, Xing S, Yashmin F, Bourassa V, Ribeiro-da-Silva A
Pain. 2020 Feb 14.
PMID: 32068663.

Abstract

It is consistently reported that in inflammatory arthritis (IA) pain may continue despite well controlled inflammation, most likely due to interactions between joint pathology and pain pathway alterations. Nervous system alterations have been described but much remains to be understood about neuronal and central non-neuronal changes in inflammatory arthritis.Using a rat model of IA induced by intra-articular CFA injection, this study includes a thorough characterization of joint pathology, and objectives to identify peripheral innervation changes and alterations in the spinal dorsal horn (DH) that could alter DH excitatory balancing. Male and female rats displayed long-lasting pain-related behavior but, in agreement with our previous studies, other pathological alterations emerged only at later times. Cartilage vascularization, thinning and decreased proteoglycan content were not detectable in the ipsilateral cartilage until 4 weeks post-CFA. Sympathetic and peptidergic nociceptive fibers invaded the ipsilateral cartilage alongside blood vessels, complex innervation changes were observed in the surrounding skin and ipsilateral NGF protein expression was increased. In the DH, we examined innervation by peptidergic and non-peptidergic nociceptors, inhibitory terminal density, the K-Cl co-transporter KCC2, microgliosis and astrocytosis. Here, we detected the presence of microgliosis and interestingly, an apparent loss of inhibitory terminals and decreased expression of KCC2.In conclusion, we found evidence of anatomical, inflammatory and neuronal alterations in the peripheral and central nervous systems in a model of inflammatory arthritis. Together these suggest that there may be a shift in the balance between incoming and outgoing excitation, and modulatory inhibitory tone in the DH.