We thank Lesley McCollum, PhD, from Liwen Bianji (Edanz) (www.liwenbianji.cn), for editing the English text of a draft of this manuscript.

The experimental protocol was approved by the Institutional Animal Care and Use Committee at Yantai University (No. YTDX20220425). The procedures followed the National Institutes of Health Guidelines for the Use of Laboratory Animals.
1. Animals
<ol>
	<li>Use ICR female mice weighing 20-25 g for the experiments.</li>
	<li>Allow the animals to acclimate to the environment of the experimental room for 3 days before starting the experiments.</li>
	<li>Maintain the experimental room with a 12-h light-dark cycle, and provide the mice with free access to water and chow.</li>
</ol>
2. Preparation of carrageenan solution
<ol>
	<li>Weigh 0.1 g of carrageenan. Add 10 mL of sterilized normal saline to a tube.</li>
	<li>Add 0.1 g of carrageenan to the tube and vortex the tube for 30 s.</li>
	<li>Collect the 1% sterilized carrageenan solution.</li>
	<li>Prepare the carrageenan solution before the experiments.</li>
</ol>
3. Intraplantar injection of carrageenan
<ol>
	<li>Use a syringe (0.05 mL, 29G x &#189; inch, 0.33 mm &#215; 12.7 mm) to inject the 1% carrageenan solution.</li>
	<li>Shake the carrageenan solution before drawing it into the syringe. Make sure that there is no bubble in the syringe.</li>
	<li>Disinfect the injection site (hind paw) with 75% alcohol.</li>
	<li>Inject 30 &#181;L6,7 of 1% carrageenan solution subcutaneously into the plantar surface of the hind paw. For the control group mice, inject 30 &#181;L of normal saline.
	<ol>
		<li>Insert the needle diagonally upwards into the hind paw foot pad. Maintain the stability of the syringe.</li>
		<li>After injection, withdraw the syringe slowly and press on the injection site for 2 s to prevent leakage.</li>
	</ol>
	</li>
</ol>
4. Hot plate test
<ol>
	<li>Conduct the hot plate test 3 h after the intraplantar injection.</li>
	<li>Clean and disinfect the surface of the hot plate.</li>
	<li>Start the hot plate apparatus. Click the Temperature Mode button. Click CONSTANT to set the temperature to 55 &#177; 0.2 &#176;C.</li>
	<li>Click Start experiment&#160;button and click REACH. Take a mouse from the accommodation container. Gently grasp its trunk. Place the mouse in the center of the hot plate. Click START.</li>
	<li>Observe and record the time to lick the left hind paw (for mice with single-hind-paw injection) or hind paw (for mice with both-hind-paw injection) in response to the heat stimulation. Press the pedal of the hot plate to see the time on the hot plate screen. Define pain threshold as the time from placing the mouse on the hot plate to licking the hind paw.</li>
	<li>Set a 60 s limit for the hot plate test4,8,9. Record a pain threshold of 60 s if the limit is reached. 
	NOTE: Clean the hot plate apparatus with 75% alcohol before placing the next mouse to avoid possible bias due to residual odor from the previous mouse.</li>
</ol>
5. Preparation of 1.5 mg/mL celecoxib suspension
<ol>
	<li>Take 1 capsule containing 200 mg celecoxib. Get the content of the capsule and grind it into a powder.</li>
	<li>Add 0.5% sodium carboxymethyl cellulose. The final volume is 13.3 mL. This is the store suspension of celecoxib.</li>
	<li>Take 1 mL of the store suspension celecoxib. Add 9.0 mL of 0.5% sodium carboxymethyl cellulose to obtain 1.5 mg/mL of celecoxib suspension.</li>
	<li>Administer 0.2 mL/10 g of the celecoxib suspension intragastrically to the mice. 
	NOTE: Select gavage needle with 4.0-4.5 cm in length for mice weighing 20-25 g.</li>
</ol>
6. Evaluating the modified inflammatory pain model
<ol>
	<li>Randomly divide ICR female mice into three groups: control, model, and celecoxib groups.</li>
	<li>Inject 30 &#181;L of 1% carrageenan solution subcutaneously into the plantar surface of the hind paw (single-hind-paw or both-hind-paw). For the control group mice, inject 30 &#181;L of normal saline.</li>
	<li>After the injection of carrageenan or normal saline, perform the treatment immediately. Intragastrically administer celecoxib at a dose of 30 mg/kg for the mice in the celecoxib group. For the mice in the control and model groups, intragastrically administer 0.5% sodium carboxymethyl cellulose.</li>
	<li>Conduct the hot plate test (section 2) at 3 h after the injection of carrageenan.</li>
</ol>
7. Statistical methods
<ol>
	<li>Present the experimental results as mean &#177; standard deviation. Conduct a normality distribution test with the Kolmogorov-Smirnov statistical goodness of fit test.</li>
	<li>Analyze the comparison between the two groups using an unpaired t-test. Perform multiple group comparisons using a one-way analysis of variance followed by Dunnett&#39;s test. Consider the value of p &#60; 0.05 statistically significant.</li>
</ol>

Dual Hind Paw Injection for Enhanced Analgesic Testing

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	<li>Deuis, J. R., Dvorakova, L. S., Vetter, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Methods+used+to+evaluate+pain+behaviors+in+rodents.">Methods used to evaluate pain behaviors in rodents.</a> Front Mol Neurosci. 10, 284 (2017).</li><li>Men&#233;ndez, L., Lastra, A., Hidalgo, A., Baamonde, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Unilateral+hot+plate+test:+a+simple+and+sensitive+method+for+detecting+central+and+peripheral+hyperalgesia+in+mice.">Unilateral hot plate test: a simple and sensitive method for detecting central and peripheral hyperalgesia in mice.</a> J Neurosci Methods. 113 (1), 91-97 (2002).</li><li>Li, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rotigotine-loaded+microspheres+exerts+the+antinociceptive+effect+via+central+dopaminergic+system.">Rotigotine-loaded microspheres exerts the antinociceptive effect via central dopaminergic system.</a> Eur J Pharmacol. 910, 174443 (2021).</li><li>Kambur, O., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Inhibitors+of+catechol-+O+-methyltransferase+sensitize+mice+to+pain.">Inhibitors of catechol- O -methyltransferase sensitize mice to pain.</a> Br J Pharmacol. 161 (7), 1553-1565 (2010).</li><li>Micheli, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Efficacy+of+Posidonia+oceanica+extract+against+inflammatory+pain:+In+vivo+studies+in+mice.">Efficacy of Posidonia oceanica extract against inflammatory pain: In vivo studies in mice.</a> Mar Drugs. 19 (2), 48 (2021).</li><li>McCarson, K. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Models+of+inflammation:+Carrageenan-+or+complete+Freund's+adjuvant+(CFA)-induced+edema+and+hypersensitivity+in+the+rat.">Models of inflammation: Carrageenan- or complete Freund's adjuvant (CFA)-induced edema and hypersensitivity in the rat.</a> Curr Protoc Pharmacol. 70, 5.4.1-5.4.9 (2015).</li><li>Fehrenbacher, J. C., Vasko, M. R., Duarte, D. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Models+of+Inflammation:+Carrageenan-+or+Complete+Freund's+Adjuvant+(CFA)-Induced+Edema+and+Hypersensitivity+in+the+Rat.">Models of Inflammation: Carrageenan- or Complete Freund's Adjuvant (CFA)-Induced Edema and Hypersensitivity in the Rat.</a> Curr Protoc Pharmacol. Chapter 5 (Unit 5.4), (2012).</li><li>Asl, M. 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The authors do not have any potential conflicting interests to disclose.

Pain is a protective response triggered by tissue damage or injury. However, it also has a negative impact on quality of life10. Therefore, the development of effective analgesics and exploration of pain mechanisms remain active areas of research. The methods for evaluating pain play a key role in the development of analgesic drugs. Single-hind-paw injection of carrageenan is a classic method for the hot plate test. The modified model induced by both-hind-paw injection of carrageenan we present he...

Pain is a public health problem worldwide. It is triggered by noxious thermal, mechanical, or chemical stimulation. It is difficult to perform pain studies in humans because of ethical concerns. Therefore, using animal pain models is a key approach to understanding pain mechanisms and research treatments1. The hot plate test has been widely used for the assessment of thermal nociception and hyperalgesia2. Currently, the model of inflammatory pain used for the hot plate test is induced with an intraplantar injection of carrageenan in one hind paw. For example, to investigate the antinociceptive effect of rotigotine-loaded microspheres, an animal model of inflammatory pain was prepared by a single-hind-paw injection3. To assess the effects of catechol-o-methyl-transferase inhibitors on thermal nociception in mice, carrageenan was administered into the plantar region of the right hind paw4. To investigate the analgesic role of the extract of Posidonia oceanica (L.) Delile, an inflammatory pain model was prepared in mice by intraplantar injection of carrageenan in the right hind paw5. However, the findings from our laboratory showed that a mouse with the single-hind-paw injection of carrageenan would lift its paw to avoid thermal nociception, which inaccurately extends the animal's response to a thermal stimulus in the hot plate test. Thus, we hypothesized that the inflammatory pain model with the single-hind-paw injection of carrageenan could not accurately reflect the thermal pain threshold. Therefore, we optimized the method by injecting carrageenan into both hind paws to establish a modified inflammatory pain model. 
The mice subjected to both-hind-paw injection of carrageenan had no way to avoid the thermal stimulus for both hind paws at the same time. The pain threshold was defined as the time from placing the mouse on the hot plate to the mouse licking either hind paw. The results confirmed that the modified inflammatory pain model is more suitable for evaluating the nociceptive temperature threshold. This may improve the efficacy of the hot plate test for the research and development of analgesic drugs.

<table><tbody><tr><td>AL204 electronic balance</td><td>Yuheng Battery Co., Ltd&amp;nbsp;</td><td>YH-400A</td><td></td></tr><tr><td>Carboxymethylcellulose</td><td>Tianjin Chemical Co., Ltd&amp;nbsp;</td><td>20210326</td><td></td></tr><tr><td>Carrageenan</td><td>Sigma, MO, USA</td><td>29H0715</td><td></td></tr><tr><td>Celecoxib</td><td>Pfizer Inc.</td><td>8142838</td><td></td></tr><tr><td>Hot plate&amp;nbsp;</td><td>UGO Ltd. Co., Italy</td><td>PB-200&amp;nbsp;</td><td></td></tr><tr><td>ICR female mice</td><td>Jinan Pengyue&amp;nbsp; Co., Ltd.</td><td>SCXK20220007</td><td></td></tr><tr><td>Normal saline</td><td>Kelun Pharmaceutical Co., Ltd&amp;nbsp;</td><td>H51021157</td><td></td></tr></tbody></table>

a modified inflammatory pain model to study the analgesic effect in mice

The hot plate test is widely used to evaluate analgesic effects on inflammatory pain in mice. A commonly used model of inflammatory pain was induced with an intraplantar injection of carrageenan in one hind paw. However, the findings from our laboratory showed that mice with a single-hind-paw injection of carrageenan lifted their paws to avoid thermal nociception during the hot plate test. Because of this response,&#160;previous injection method cannot accurately reflect the thermal pain threshold. Thus, we investigated a new method to avoid this issue. In the present study, we modified the previous method by injecting carrageenan into both hind paws to establish the model of inflammatory pain. The results demonstrated that both-hind-paw injection with carrageenan was sensitive and a better method to induce inflammatory pain when using the hot plate test than single-hind-paw injection. On the basis of these findings, we designed further experiments in which mice with either both-hind-paw or single-hind-paw injection of carrageenan were treated intragastrically with celecoxib (30 mg/kg). The results of the hot plate test showed that celecoxib augmented the thermal pain threshold in mice with both-hind-paw injection of carrageenan but not in mice with single-hind-paw injection of carrageenan. In summary, we developed a superior method to induce a model of inflammatory pain to evaluate analgesic effect.

The pain threshold in inflammatory pain models 
The pain threshold of the inflammatory pain model with single-hind-paw injection of carrageenan was 32.23 &#177; 11.11&#160;s, whereas the pain threshold of the control group was 27.73 &#177; 7.08&#160;s. Compared with the control group, the pain threshold of the single-hind-paw injection model did not show a significant reduction (p &#62; 0.05, Figure 1A). The pain threshold of the inflammatory pain model with both-hind-p...

Author Spotlight: Enhanced Method for Evaluating Analgesic Effects &#8212; Dual Hind Paw Carrageenan Injection in Mice

Here, we present a modified inflammatory pain model with the both-hind-paw carrageenan injection to evaluate the analgesic effect.

A Modified Inflammatory Pain Model to Study the Analgesic Effect in Mice

The hot plate test is widely used to evaluate analgesic effects on inflammatory pain in mice. A commonly used model of inflammatory pain was induced with ...

a-modified-inflammatory-pain-model-to-study-analgesic-effect

Universidad de Cartagena UDEC

Research

JoVE Journal

Neuroscience

1.3K Views.  Yantai University. Here, we present a modified inflammatory pain model with the both-hind-paw carrageenan injection to evaluate the analgesic effect.

Video: Author Spotlight: Enhanced Method for Evaluating Analgesic Effects — Dual Hind Paw Carrageenan Injection in Mice

The Sciatic Nerve Cuffing Model of Neuropathic Pain in Mice

Neuropathic pain arises as a consequence of a lesion or a disease affecting the somatosensory system. This syndrome results from maladaptive changes in injured sensory neurons and along the entire nociceptive pathway within the central nervous system. It is usually chronic and challenging to treat. In order to study neuropathic pain and its treatments, different models have been developed in rodents. These models derive from known etiologies, thus reproducing peripheral nerve injuries, central injuries, and metabolic-, infectious- or chemotherapy-related neuropathies. Murine models of peripheral nerve injury often target the sciatic nerve which is easy to access and allows nociceptive tests on the hind paw. These models rely on a compression and/or a section. Here, the detailed surgery procedure for the &#34;cuff model&#34; of neuropathic pain in mice is described. In this model, a cuff of PE-20 polyethylene tubing of standardized length (2 mm) is unilaterally implanted around the main branch of the sciatic nerve. It induces a long-lasting mechanical allodynia, i.e., a nociceptive response to a normally non-nociceptive stimulus that can be evaluated by using von Frey filaments. Besides the detailed surgery and testing procedures, the interest of this model for the study of neuropathic pain mechanism, for the study of neuropathic pain sensory and anxiodepressive aspects, and for the study of neuropathic pain treatments are also discussed.

Neuropathic pain is a consequence of a lesion or disease affecting the somatosensory system. The &#8220;cuff model&#8221; of neuropathic pain in mice consists of the implantation of a polyethylene cuff around the main branch of the sciatic nerve. Mechanical allodynia is tested using von Frey filaments.

Neuropathic pain arises as a consequence of a lesion or a disease affecting the somatosensory system. This syndrome results from maladaptive changes in ...

Medicine

Assessment of Morphine-induced Hyperalgesia and Analgesic Tolerance in Mice Using Thermal and Mechanical Nociceptive Modalities

Opioid-induced hyperalgesia and tolerance severely impact the clinical efficacy of opiates as pain relievers in animals and humans. The molecular mechanisms underlying both phenomena are not well understood and their elucidation should benefit from the study of animal models and from the design of appropriate experimental protocols. 
We describe here a methodological approach for inducing, recording and quantifying morphine-induced hyperalgesia as well as for evidencing analgesic tolerance, using the tail-immersion and tail pressure tests in wild-type mice. As shown in the video, the protocol is divided into five sequential steps. Handling and habituation phases allow a safe determination of the basal nociceptive response of the animals. Chronic morphine administration induces significant hyperalgesia as shown by an increase in both thermal and mechanical sensitivity, whereas the comparison of analgesia time-courses after acute or repeated morphine treatment clearly indicates the development of tolerance manifested by a decline in analgesic response amplitude. This protocol may be similarly adapted to genetically modified mice in order to evaluate the role of individual genes in the modulation of nociception and morphine analgesia. It also provides a model system to investigate the effectiveness of potential therapeutic agents to improve opiate analgesic efficacy.

We describe a protocol to examine the development of opioid-induced hyperalgesia and tolerance in mice. Based on the measurement of thermal and mechanical nociceptive responses of na&#239;ve and morphine-treated animals, it allows to quantify the increase in pain sensitivity (hyperalgesia) and decrease in analgesia (tolerance) associated with chronic opiate administration.

Opioid-induced hyperalgesia and tolerance severely impact the clinical efficacy of opiates as pain relievers in animals and humans. The molecular ...

Urokinase-type Plasminogen Activator-induced Mouse Back Pain Model

A model of persisting lower back pain can be induced in mice with the simple methodology described herein. Step-by-step methods for simple, rapid induction of a persisting back pain model in mice are provided here using an injection of urokinase-type plasminogen activator (urokinase), a serine protease present in humans and other animals. The methodology for induction of persisting lower back pain in mice involves a simple injection of urokinase along the ligamentous insertion region of the lumbar spine. The urokinase inflammatory agent activates plasminogen to plasmin. Typically, the model can be induced within 10 min and hypersensitivity persists for at least 8 weeks.
Hypersensitivity, gait disturbance, and other standard anxiety- and depression-like measures can be tested in the persisting model.&#160;Back pain is the most prevalent type of pain. To improve awareness of back pain, the International Association for the Study of Pain (IASP) named 2021 the &#34;Global Year about Back Pain&#34; and 2022 the &#34;Global Year for Translating Pain Knowledge to Practice.&#34; One limitation of the therapeutic advancement of pain therapeutics is the lack of suitable models for testing persistent and chronic pain. The&#160;features of this model&#160;are suitable for testing potential therapeutics aimed at the reduction of back pain and its ancillary characteristics, contributing to IASP&#39;s naming 2022 as the Global Year for Translating Pain Knowledge to Practice.

Methods for simple, rapid induction of a back pain model in mice are provided here using an intraligament injection of urinary plasminogen activator.

A model of persisting lower back pain can be induced in mice with the simple methodology described herein. Step-by-step methods for simple, rapid ...

Behavior

The Monoiodoacetate Model of Osteoarthritis Pain in the Mouse

A major symptom of patients with osteoarthritis (OA) is pain that&#160;is triggered by peripheral as well as central changes within the pain pathways. The current treatments for OA pain such as NSAIDS or opiates are neither sufficiently effective nor devoid of detrimental side effects. Animal models of OA are being developed to improve our understanding of OA-related pain mechanisms and define novel pharmacological targets for therapy. Currently available models of OA in rodents include surgical and chemical interventions into one knee joint. The monoiodoacetate (MIA) model has become a standard for modelling joint disruption in OA in both rats and mice. The model, which is easier to perform in the rat, involves injection of MIA into a knee joint that induces rapid pain-like responses in the ipsilateral limb, the level of which can be controlled by injection of different doses. Intra-articular injection of MIA disrupts chondrocyte glycolysis by inhibiting glyceraldehyde-3-phosphatase dehydrogenase and results in chondrocyte death, neovascularization, subchondral bone necrosis and collapse, as well as inflammation. The morphological changes of the articular cartilage and bone disruption are reflective of some aspects of patient pathology. Along with joint damage, MIA injection induces referred mechanical sensitivity in the ipsilateral hind paw and weight bearing deficits that are measurable and quantifiable. These behavioral changes resemble some of the symptoms reported by the patient population, thereby validating the MIA injection in the knee as a useful and relevant pre-clinical model of OA pain.
The aim of this article is to describe the methodology of intra-articular injections of MIA and the behavioral recordings of the associated development of hypersensitivity with a mind to highlight the necessary steps to give consistent and reliable recordings.

Osteoarthritis (OA), or degenerative joint disease, is a debilitating condition associated with pain that remains only partially controlled by available analgesics. Animal models are being developed to improve our understanding of OA-related pain mechanisms. Here we describe the methodology for the monoiodoacetate model of OA pain in the mouse.

A major symptom of patients with osteoarthritis (OA) is pain that&#160;is triggered by peripheral as well as central changes within the pain pathways. The ...

Development of Recombinant Proteins to Treat Chronic Pain

Chronic pain is difficult to treat and new approaches to resolve persistent pain are urgently needed. Anti-inflammatory cytokines are promising candidates for treating debilitating pain conditions due to their capacity to regulate aberrant neuro-immune interactions. However, physiologically they work in a network of various cytokines, and therefore their therapeutic effect may not be optimal when used as stand-alone drugs. To overcome this limitation, we developed a fusion protein of the anti-inflammatory cytokines IL4 and IL10. Here, we describe the methods for production and quality control of IL4-10 recombinant fusion protein and we test the effectiveness of the IL4-10 fusion protein to resolve pain in a mouse model of persistent inflammatory pain.

In this paper we provide details for the methods of production and quality control of an IL4-10 recombinant fusion protein. We also show how to test the effectiveness of this protein to resolve pain in a mouse model of inflammatory pain.

Chronic pain is difficult to treat and new approaches to resolve persistent pain are urgently needed. Anti-inflammatory cytokines are promising candidates ...

Spontaneous and Evoked Measures of Pain in Murine Models of Monoarticular Knee Pain

Pain is the main cause of disability from arthritis. There is currently an unmet need for adequate treatments for arthritis pain. Pre-clinical models are necessary and useful for studying the mechanisms of pain and for evaluating efficacy of arthritis therapies. Measuring pain in animal models of arthritis is challenging. We have developed methods for measuring evoked and spontaneous pain in three models of murine arthritis. We quantitate the evoked pain responses of mice subjected to firm palpation of a painful knee. We also evaluate spontaneous pain by the proportion of weight and the amount of time placed on each of their 4 limbs after induction of arthritis pain in one knee. Joint pain in these mouse models produces a significant increase in evoked pain responses and an alteration in weight bearing. Since mice are quadrupeds, they offload the painful limb to the contralateral limb, to the forelimbs, or some combination. These methods are simple, require minimal equipment, and are reproducible and sensitive for detecting pain. They are useful for studying both disease-modifying arthritis treatments and analgesics in mice.

We have developed an evoked measure of arthritis pain and coupled it with a standardized method for measuring spontaneous pain in different murine models of chemically induced arthritis. These measures are sensitive and reproducible for different types of joint pain.

Pain is the main cause of disability from arthritis. There is currently an unmet need for adequate treatments for arthritis pain. Pre-clinical models are ...

Modified Spared Nerve Injury Surgery Model of Neuropathic Pain in Mice

Spared nerve injury (SNI) is an animal model that mimics the cardinal symptoms of peripheral nerve injury for studying the molecular and cellular mechanism of neuropathic pain in mice and rats. Currently, there are two types of SNI model, one to cut and ligate the common peroneal and the tibial nerves with intact sural nerve, which is defined as SNIs in this study, and another to cut and ligate the common peroneal and the sural nerves with intact tibial nerve, which is defined as SNIt in this study. Because the sural nerve is purely sensory whereas the tibial nerve contains both motor and sensory fibers, the SNIt model has much less motor deficit than the SNIs model. In the traditional SNIt mouse model, the common peroneal and the sural nerves are cut and ligated separately. Here a modified SNIt surgery method is described to damage both common peroneal and sural nerves with only one ligation and one cut with a shorter procedure time, which is easier to perform and reduces the potential risk of stretching the sciatic or tibial nerves, and produces similar mechanical hypersensitivity as the traditional SNIt model.

The modified surgery is a simplified method for mouse or rat spared nerve injury model that requires only one ligation and one cut to injure both common peroneal and sural nerves.

Spared nerve injury (SNI) is an animal model that mimics the cardinal symptoms of peripheral nerve injury for studying the molecular and cellular ...

Mechanical Conflict-Avoidance Assay to Measure Pain Behavior in Mice

Pain comprises of both sensory (nociceptive) and affective (unpleasant) dimensions. In preclinical models, pain has traditionally been assessed using reflexive tests that allow inferences regarding pain's nociceptive component but provide little information about the affective or motivational component of pain. Developing tests that capture these components of pain are therefore translationally important. Hence, researchers need to use non-reflexive behavioral assays to study pain perception at that level. Mechanical conflict-avoidance (MCA) is an established voluntary non-reflexive behavior assay, for studying motivational responses to a noxious mechanical stimulus in a 3 chamber paradigm. A change in a mouse's location preference, when faced with competing noxious stimuli, is used to infer the perceived unpleasantness of bright light versus tactile stimulation of the paws. This protocol outlines a modified version of the MCA assay which pain researchers can use to understand affective-motivational responses in a variety of mouse pain models. Though not specifically described here, our example MCA data use the intraplantar complete Freund's adjuvant (CFA), spared nerve injury (SNI), and a fracture/casting model as pain models to illustrate the MCA procedure.

The mechanical conflict-avoidance assay is used as a non-reflexive readout of pain sensitivity in mice which can be used to better understand affective-motivational responses in a variety of mouse pain models.

Pain comprises of both sensory (nociceptive) and affective (unpleasant) dimensions. In preclinical models, pain has traditionally been assessed using ...

Partial Sciatic Nerve Ligation: A Mouse Model of Chronic Neuropathic Pain to Study the Antinociceptive Effect of Novel Therapies

Management of chronic pain remains challenging to this day, and current treatments are associated with adverse effects, including tolerance and addiction. Chronic neuropathic pain results from lesions or diseases in the somatosensory system. To investigate potential therapies with reduced side effects, animal pain models are the gold standard in preclinical studies. Therefore, well-characterized and well-described models are crucial for the development and validation of innovative therapies. 
Partial ligation of the sciatic nerve (pSNL) is a procedure that induces chronic neuropathic pain in mice, characterized by mechanical and thermal hypersensitivity, ongoing pain, and changes in limb temperature, making this model a great fit to study neuropathic pain preclinically. pSNL is an advantageous model to study neuropathic pain as it reproduces many symptoms observed in humans with neuropathic pain. Furthermore, the surgical procedure is relatively fast and straightforward to perform. Unilateral pSNL of one limb allows for comparison between the ipsilateral and contralateral paws, as well as evaluation of central sensitization. 
To induce chronic neuropathic hypersensitivity, a 9-0 non-absorbable nylon thread is used to ligate the dorsal third of the sciatic nerve. This article describes the surgical procedure and characterizes the development of chronic neuropathic pain through multiple commonly used behavioral tests. As a plethora of innovative therapies are now being investigated to treat chronic pain, this article provides crucial concepts for standardization and an accurate description of surgeries required to induce neuropathic pain.

Partial sciatic nerve ligation induces long-lasting chronic neuropathic pain, characterized by exaggerated responses to thermal and mechanical stimuli. This mouse model of neuropathic pain is commonly used to study innovative therapies for pain management. This article describes in detail the surgical procedure to improve standardization and reproducibility.

Management of chronic pain remains challenging to this day, and current treatments are associated with adverse effects, including tolerance and addiction. ...

Standardized Tuina Protocol for Rat DRG Compression Model

Analgesic Effect of Tuina on Rat Models with Compression of the Dorsal Root Ganglion Pain

Neuropathic pain is a prevalent condition that affects 6.9%-10% of the population and results from nerve damage due to various etiologies, such as lumbar disc herniation, spinal canal stenosis, and intervertebral foramen stenosis. Although Tuina, a traditional Chinese manual therapy, has shown analgesic effects in clinical practice for the treatment of neuropathic pain, its underlying neurobiological mechanisms remain unclear. Animal models are essential for elucidating the basic principles of Tuina. In this study, we propose a standardized Tuina protocol for rats with compression of the dorsal root ganglion (DRG), which involves inducing DRG compression by inserting a stainless steel rod into the intervertebral foramen, performing Tuina manipulation with specific parameters of location, intensity, and frequency in a controlled environment, and assessing the behavioral and histopathological outcomes of Tuina treatment. This article also discusses the potential clinical implications and limitations of the study and suggests directions for future research on Tuina.

Author Spotlight: Analgesic Effect of Tuina on Rat Models with Compression of the Dorsal Root Ganglion Pain  

This article presents a manipulation for treating chronic compression of the dorsal root ganglion in rats using Tuina therapy, along with a method for evaluating its effectiveness based on pain behavior and histopathological results.

Neuropathic pain is a prevalent condition that affects 6.9%-10% of the population and results from nerve damage due to various etiologies, such as lumbar ...