Modulation of the gait deficit in arthritic rats by infusions of muscimol and bicuculline

Evaluation of the GABAA Receptor Expression and the Effects of Muscimol on the Activity of Wide Dynamic Range Neurons Following Chronic Constriction Injury of Sciatic Nerve in Rats

Introduction

The modality of γ-aminobutyric acid type a receptors (GABAA) controls dorsal horn neuronal excitability and inhibits sensory information. This study aimed to investigate the expression of the GABAA receptor and the effects of its agonist muscimol on Wide Dynamic Range (WDR) neuronal activity in the Chronic Constriction Injury (CCI) model of neuropathic pain.

Methods

Adult male Wistar rats weighing 200 to 250 g were used to induce CCI neuropathy. Fourteen days after surgery, muscimol (0.5, 1, and 2 mg/kg IP) was injected. Then, the behavioral tests were performed. After that, the animals were killed, and the lumbar segments of the spinal cords were collected for Western blot analysis of the GABAA receptor α1 subunit expression. The electrophysiological properties of WDR neurons were studied by single-unit recordings in separate groups 14 days after CCI.

Results

The outcomes indicated the development of thermal hyperalgesia and mechanical allodynia after neuropathy; nonetheless, the expression of the GABAA receptor α1 subunit did not change significantly. Moreover, the evoked responses of the WDR neurons to electrical, mechanical, and thermal stimuli increased considerably. Fourteen days after CCI, muscimol administration decreased thermal hyperalgesia, mechanical allodynia, and hyper-responsiveness of the WDR neurons in CCI rats.

Conclusion

The modulation of the spinal GABAA receptors after nerve injury can offer further insights to design new therapeutic agents to reduce neuropathic pain symptoms.

Gait analysis methods for rodent models of arthritic disorders: reviews and recommendations

Gait analysis is a useful tool to understand behavioral changes in preclinical arthritis models. While observational scoring and spatiotemporal gait parameters are the most widely performed gait analyses in rodents, commercially available systems can now provide quantitative assessments of spatiotemporal patterns. However, inconsistencies remain between testing platforms, and laboratories often select different gait pattern descriptors to report in the literature. Rodent gait can also be described through kinetic and kinematic analyses, but systems to analyze rodent kinetics and kinematics are typically custom made and often require sensitive, custom equipment. While the use of rodent gait analysis rapidly expands, it is important to remember that, while rodent gait analysis is a relatively modern behavioral assay, the study of quadrupedal gait is not new. Nearly all gait parameters are correlated, and a collection of gait parameters is needed to understand a compensatory gait pattern used by the animal. As such, a change in a single gait parameter is unlikely to tell the full biomechanical story; and to effectively use gait analysis, one must consider how multiple different parameters contribute to an altered gait pattern. The goal of this article is to review rodent gait analysis techniques and provide recommendations on how to use these technologies in rodent arthritis models, including discussions on the strengths and limitations of observational scoring, spatiotemporal, kinetic, and kinematic measures. Recognizing rodent gait analysis is an evolving tool, we also provide technical recommendations we hope will improve the utility of these analyses in the future.

Cartilage damage and bone erosion are more prominent determinants of functional impairment in longstanding experimental arthritis than synovial inflammation

Chronic inflammation of articular joints causing bone and cartilage destruction consequently leads to functional impairment or loss of mobility in affected joints from individuals affected by rheumatoid arthritis (RA). Even successful treatment with complete resolution of synovial inflammatory processes does not lead to full reversal of joint functionality, pointing to the crucial contribution of irreversibly damaged structural components, such as bone and cartilage, to restricted joint mobility. In this context, we investigated the impact of the distinct components, including synovial inflammation, bone erosion or cartilage damage, as well as the effect of blocking tumor necrosis factor (TNF) on functional impairment in human-TNF transgenic (hTNFtg) mice, a chronic inflammatory erosive animal model of RA. We determined CatWalk-assisted gait profiles as objective quantitative measurements of functional impairment. We first determined body-weight-independent gait parameters, including maximum intensity, print length, print width and print area in wild-type mice. We observed early changes in those gait parameters in hTNFtg mice at week 5 – the first clinical signs of arthritis. Moreover, we found further gait changes during chronic disease development, indicating progressive functional impairment in hTNFtg mice. By investigating the association of gait parameters with inflammation-mediated joint pathologies at different time points of the disease course, we found a relationship between gait parameters and the extent of cartilage damage and bone erosions, but not with the extent of synovitis in this chronic model. Next, we observed a significant improvement of functional impairment upon blocking TNF, even at progressed stages of disease. However, blocking TNF did not restore full functionality owing to remaining subclinical inflammation and structural microdamage. In conclusion, CatWalk gait analysis provides a useful tool for quantitative assessment of functional impairment in inflammatory destructive arthritis. Our findings indicate that cartilage damage and bone erosion, but not synovial inflammation, are the most important determinants for progressive functional impairment in this chronic erosive arthritis model.

Summary: Gait-profile assessment is an objective quantitative measurement to monitor functional impairment in arthritis models. Longstanding functional impairment correlates with inflammation-driven structural damage.

Direct radiofrequency application improves pain and gait in collagenase-induced acute achilles tendon injury

Radiofrequency (RF) is often used as a supplementary and alternative method to alleviate pain for chronic tendinopathy. Whether or how it would work for acute tendon injury is not addressed in the literatures. Through detailed pain and gait monitoring, we hypothesized that collagenase-induce acute tendinopathy model may be able to answer these questions. Gait parameters, including time, distance, and range of motion, were recorded and analyzed using a walking track equipped with a video-based system. Expression of substance P (SP), calcitonin gene related peptide (CGRP), and galanin were used as pain markers. Beta-III tubulin and Masson trichrome staining were used as to evaluate nerve sprouting, matrix tension, and degeneration in the tendon. Of fourteen analyzed parameters, RF significantly improved stance phase, step length, preswing, and intermediary toe-spread of gait. Improved gait related to the expression of substance P, CGRP, and reduced nerve fiber sprouting and matrix tension, but not galanin. The study indicates that direct RF application may be a valuable approach to improve gait and pain in acute tendon injury. Altered gait parameters may be used as references to evaluate therapeutic outcomes of RF or other treatment plan for tendinopathy.

The anti-arthritic and immune-modulatory effects of NHAG: a novel glucosamine analogue in adjuvant-induced arthritis

Rheumatoid arthritis (RA) is potentially devastating condition which lacks good treatment options. Pro-inflammatory cytokines interleukin-1beta (IL-1β), tumor necrosis factor-alpha (TNF-α), and oxidative stress markers such as nitric oxide (NO) and peroxide (PO) are mediators of RA pathogenesis. In the present study N-[2,4,5-trihydroxy-6-(hydroxymethyl) tetrahydro-2H-pyran-3-yl]acrylamide (NHAG), analogue of glucosamine, was evaluated in adjuvant-induced arthritic model of rats. The disease progression was monitored by analysing arthritis scoring, loss of body weight, paw oedema, and histological changes in joints. RA associated hyperalgesia was evaluated by gait analysis. The serum or plasma levels of NO, PO, glutathione (GSH) superoxide dismutase (SOD) IL-1β and TNF-α were analyzed to monitor the state of disease severity. The arthritic control animals exhibited significant increase in arthritic score (P < 0.003) and paw oedema (P < 0.001) with parallel loss in body weight (P < 0.04). The NHAG-treated arthritic animals exhibited refinement in the gait changes associated with arthritis. NHAG also significantly decreased the NO (P < 0.02) and PO (P < 0.03) with concurrent increased in GSH (P < 0.04) and SOD (P < 0.007). Both IL-1β (P < 0.001) and TNF-α (P < 0.001), were significantly decreased in NHAG-treated group. Thus NHAG might have a therapeutic potential for arthritis by exerting antioxidative and immunomodulatory effects.

Gait analysis in rats with single joint inflammation: influence of experimental factors

Disability and movement-related pain are major symptoms of joint disease, motivating the development of methods to quantify motor behaviour in rodent joint pain models. We used observational scoring and automated methods to compare weight bearing during locomotion and during standing after single joint inflammation induced by Freund's complete adjuvant (0.12–8.0 mg/mL) or carrageenan (0.47–30 mg/mL). Automated gait analysis was based on video capture of prints generated by light projected into the long edge of the floor of a walkway, producing an illuminated image of the contact area of each paw with light intensity reflecting the contact pressure. Weight bearing was calculated as an area-integrated paw pressure, that is, the light intensity of all pixels activated during the contact phase of a paw placement. Automated static weight bearing was measured with the Incapacitance tester. Pharmacological sensitivity of weight-bearing during locomotion was tested in carrageenan-induced monoarthritis by administration of the commonly used analgesics diclofenac, ibuprofen, and naproxen, as well as oxycodone and paracetamol. Observational scoring and automated quantification yielded similar results. We found that the window between control rats and monoarthritic rats was greater during locomotion. The response was more pronounced for inflammation in the ankle as compared to the knee, suggesting a methodological advantage of using this injection site. The effects of both Freund's complete adjuvant and carrageenan were concentration related, but Freund's incomplete adjuvant was found to be as effective as lower, commonly used concentrations of the complete adjuvant. The results show that gait analysis can be an effective method to quantify behavioural effects of single joint inflammation in the rat, sensitive to analgesic treatment.

Videoradiographic analysis of the range of motion in unilateral experimental knee joint arthritis in rats

Introduction

The translational and predictive value of animal models highly depends on the validity of respective readout parameters. In arthritis research, there has been a shift from sole threshold testing for pain-related behavior, as well as from swelling and histology assessment for inflammation, toward an analysis of joint function as indicated, for instance, by an increasing number of studies on gait abnormalities. Clinically, the range of motion (ROM) of the affected joint plays a major role in diagnosis and the assessment of treatment benefits. This parameter, however, is only insufficiently detected by currently used analytic systems in animals.

Methods

Here we used high-resolution videoradiographic analysis to assess ROM in experimental knee joint arthritis in rats. This parameter is described during the 21-day course of antigen-induced arthritis in rats. Furthermore, the therapeutic effects of antinociceptive (morphine) and anti-inflammatory (dexamethasone) treatment on ROM are documented. To obtain additional information on the implications of ROM in animal models, correlations were performed to measure pain-related behavior and inflammation.

Results

The study animals showed a significant reduction in ROM of the inflamed knee joint in the acute phase of arthritis. This was accompanied by an increase in knee joint movement on the contralateral side, indicating a compensational mechanism. Both morphine and dexamethasone treatment increased and thus normalized ROM. Changes in ROM were further stage-dependently correlated with weight bearing and joint swelling, that is, with both pain-related behavior and signs of inflammation.

Conclusions

The dynamic ROM observed in freely moving rats in our model of knee joint arthritis might serve as a parameter for global disease activity and might thus represent a promising readout parameter for preclinical assessment regarding the overall efficacy not only of antiarthritic but also of antinociceptive compounds.

Hypolocomotion, asymmetrically directed behaviors (licking, lifting, flinching, and shaking) and dynamic weight bearing (gait) changes are not measures of neuropathic pain in mice

BACKGROUND

Spontaneous (non-evoked) pain is a major clinical symptom of neuropathic syndromes, one that is understudied in basic pain research for practical reasons and because of a lack of consensus over precisely which behaviors reflect spontaneous pain in laboratory animals. It is commonly asserted that rodents experiencing pain in a hind limb exhibit hypolocomotion and decreased rearing, engage in both reflexive and organized limb directed behaviors, and avoid supporting their body weight on the affected side. Furthermore, it is assumed that the extent of these positive or negative behaviors can be used as a dependent measure of spontaneous chronic pain severity in such animals. In the present study, we tested these assumptions via blinded, systematic observation of digital video of mice with nerve injuries (chronic constriction or spared nerve injury), and automated assessment of locomotor behavior using photocell detection and dynamic weight bearing (i.e., gait) using the CatWalk system.

RESULTS

We found no deficits in locomotor activity or rearing associated with neuropathic injury. The frequency of asymmetric (ipsilaterally directed) behaviors were too rare to be seriously considered as representing spontaneous pain, and in any case did not statistically exceed what was blindly observed on the contralateral hind paw and in control (sham operated and unoperated) mice. Changes in dynamic weight bearing, on the other hand, were robust and ipsilateral after spared nerve injury (but not chronic constriction injury). However, we observed timing, pharmacological, and genetic dissociation of mechanical allodynia and gait alterations.

CONCLUSIONS

We conclude that spontaneous neuropathic pain in mice cannot be assessed using any of these measures, and thus caution is warranted in making such assertions.

Gait changes precede overt arthritis and strongly correlate with symptoms and histopathological events in pristane-induced arthritis

INTRODUCTION

Pristane-induced arthritis (PIA) in the rat has been described as an animal model of inflammatory arthritis which exhibits features similar to rheumatoid arthritis in humans, such as a chronic, destructive, and symmetrical involvement of peripheral joints. However, so far little is known about the earliest inflammatory events and their influence on locomotor behaviour during the course of PIA. To investigate this issue a detailed analysis of the pathologic changes occurring during the prodromal and early stages of PIA was performed.

METHODS

Arthritis was induced in DA.rats by injection of 150 microl 2,6,10,4-tetramethyl-pentadecane (pristane) at the base of the tail and changes in locomotor behaviour of the affected paws were monitored using the CatWalk quantitative gait analysis system. The pathologic events occurring in the joints of pristane-injected animals were studied before onset, at onset, and during acute phase of arthritis by histological methods.

RESULTS

Gait analysis revealed that changes in locomotion such as reduced paw print areas and stance phase time are already apparent before the onset of clinically discernible arthritis symptoms (erythema, paw swelling) and correlate with PIA scores. In agreement with these findings, inflammatory tenosynovitis could be observed by histology already before the onset of erythema and swelling of the respective paws. In the most heavily affected rats also irregularities in step sequence patterns occurred A kinetic analysis of clinical and histological findings demonstrated that gait changes precede the pathological changes occurring during the acute phase of pristane-induced arthritis.

CONCLUSIONS

Gait analysis allows for pinpointing the initial inflammatory changes in experimental arthritis models such as pristane-induced arthritis. Analysis of early clinically relevant symptoms in arthritis models may facilitate the search for novel therapeutics to interfere with pain, inflammation and joint destruction in patients suffering from inflammatory arthritis.

Quantitative gait analysis as a method to assess mechanical hyperalgesia modulated by disease-modifying antirheumatoid drugs in the adjuvant-induced arthritic rat

In the present study, azothioprine, chloroquine, D-penicillamine, methotrexate and sodium aurothiomalate (gold salt) were evaluated for possible disease-modifying effects in the adjuvant-induced arthritis model of human rheumatoid arthritis in rats. Gait analysis was used to examine the role of disease-modifying antirheumatic drugs in the development of pain. Body weights were also measured to monitor the progression of disease and the systemic antiarthritic effects of the test compounds used in this study, as well as their systemic toxicity. Our results showed that azothioprine (5 mg/kg/day), chloroquine (12.5 mg/kg/day), sodium aurothiomalate (2.5 mg/kg/day) and methotrexate (1 mg/kg/week) not only inhibited the macroscopic changes such as erythema and swelling of limbs, but also exhibited significant reversal of gait deficits seen in the untreated or saline-treated arthritic rats. No reduction in the body weights were observed in the arthritic rats treated with azothioprine, chloroquine, sodium aurothiomalate and methotrexate. D-Penicillamine (12.5 mg/kg/day), however, showed a significant reduction (P < 0.03) in the body weights of the arthritic rats over a period of 22 days; furthermore, it was unable to show any reduction in arthritic score (P < 0.1). In earlier experiments, chloroquine and methotrexate failed to suppress carageenan-induced edema, suggesting that the mode of antiarthritic action may be different from those of nonsteroidal anti-inflammatory agents. Since these disease-modifying antirheumatic drugs are reported to have an immunomodulatory role, especially the gold salt, which influences the monocyte–macrophage system, it is suggested that the observed antiarthritic effects of disease-modifying antirheumatic drugs may be partly attributed to their immunomodulatory activity.

Gait analysis in a murine model of collagen-induced arthritis

Murine collagen-induced arthritis (CIA) has become a valuable animal model for elucidating pathogenic mechanisms and evaluating therapeutic effects for rheumatoid arthritis. Recent advances in digital imaging and computer technology have enabled gait analysis to develop into a powerful tool for objectively detecting functional deficits in human and animal models. The present study explored the use of non-invasive video-capture gait analysis in the evaluation of a murine CIA model. CIA was induced in 45 female DBA/1LacJ mice (8 to 10 weeks old) by immunization with lyophilized bovine articular type II collagen. Gait parameters were determined by ventral plane videography and were correlated to traditional arthritis clinical scores. Our results showed that increases in clinical scores that measure the severity of CIA corresponded to changes in multiple gait parameters that reflect both morphologic (increases in paw area) and functional (increase in stride frequency, decrease in stride length, hind-limb paw placement angle, as well as stride, stance, and braking times) deficits. Our work indicated that the non-invasive video-capture device may be used as a simple and objective data acquisition system for quantifying gait disturbances in CIA mice for the investigation of mechanisms and the evaluation of therapeutic agents.