Grant funding was provided by NIH HEAL UG3 NS123958. The housing facilities were inspected and accredited by AAALAC. Animals were housed in the Animal Resources Center (ARC) housing facility maintained by the laboratory staff and Division of Laboratory and Animal Resources (DLAR) staff. The procedures for behavioral testing are standard methods in the field as approved by the American Pain Society and the International Association for the Study of Pain. The method of euthanasia is consistent with recommendations of the Panel on Euthanasia of the American Veterinary Medical Association.

<ol>
	<li>O'Sullivan, P. B., 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=Back+to+basics:+10+facts+every+person+should+know+about+back+pain.">Back to basics: 10 facts every person should know about back pain.</a> British Journal of Sports Medicine. 54 (12), 698-699 (2020).</li><li>Nauta, H. J., McIlwrath, S. L., Westlund, K. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Punctate+midline+myelotomy+reduces+pain+responses+in+a+rat+model+of+lumbar+spine+pain:+evidence+that+the+postsynaptic+dorsal+column+pathway+conveys+pain+from+the+axial+spine.">Punctate midline myelotomy reduces pain responses in a rat model of lumbar spine pain: evidence that the postsynaptic dorsal column pathway conveys pain from the axial spine.</a> Cureus. 10 (3), 2371 (2018).</li><li>Shuang, F., 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=Establishment+of+a+rat+model+of+lumbar+facet+joint+osteoarthritis+using+intraarticular+injection+of+urinary+plasminogen+activator.">Establishment of a rat model of lumbar facet joint osteoarthritis using intraarticular injection of urinary plasminogen activator.</a> Scientific Reports. 5 (1), 9828 (2015).</li><li>Reed, N. R., 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=Somatosensory+behavioral+alterations+in+a+NGF-induced+persistent+low+back+pain+model.">Somatosensory behavioral alterations in a NGF-induced persistent low back pain model.</a> Behavioural Brain Research. 418, 113617 (2022).</li><li>Suh, H. R., Cho, H. -. Y., Han, H. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+of+a+novel+model+of+intervertebral+disc+degeneration+by+the+intradiscal+application+of+monosodium+iodoacetate+(MIA)+in+rat.">Development of a novel model of intervertebral disc degeneration by the intradiscal application of monosodium iodoacetate (MIA) in rat.</a> The Spine Journal. 22 (1), 183-192 (2022).</li><li>Kim, H., Hong, J. Y., Lee, J., Jeon, W. -. J., Ha, I. -. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=IL-1&#946;+promotes+disc+degeneration+and+inflammation+through+direct+injection+of+intervertebral+disc+in+a+rat+lumbar+disc+herniation+model.">IL-1&#946; promotes disc degeneration and inflammation through direct injection of intervertebral disc in a rat lumbar disc herniation model.</a> The Spine Journal. 21 (6), 1031-1041 (2021).</li><li>Millecamps, M., Tajerian, M., Sage, E. H., Stone, L. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Behavioral+signs+of+chronic+back+pain+in+the+SPARC-null+mouse.">Behavioral signs of chronic back pain in the SPARC-null mouse.</a> Spine. 36 (2), 95-102 (2011).</li><li>La Porta, C., Tappe-Theodor, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Differential+impact+of+psychological+and+psychophysical+stress+on+low+back+pain+in+mice.">Differential impact of psychological and psychophysical stress on low back pain in mice.</a> Pain. 161 (7), 1442-1458 (2020).</li><li>Chaplan, S. R., Bach, F. W., Pogrel, J. W., Chung, J. M., Yaksh, T. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quantitative+assessment+of+tactile+allodynia+in+the+rat+paw.">Quantitative assessment of tactile allodynia in the rat paw.</a> Journal of Neuroscience Methods. 53 (1), 55-63 (1994).</li><li>Takao, K., Miyakawa, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Light/dark+transition+test+for+mice.">Light/dark transition test for mice.</a> Journal of Visualized Experiments JoVE. (1), e104 (2006).</li><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> Frontiers in Molecular Neuroscience. 10, 284 (2017).</li><li>David, D. J., 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=Neurogenesis-dependent+and+-independent+effects+of+fluoxetine+in+an+animal+model+of+anxiety/depression.">Neurogenesis-dependent and -independent effects of fluoxetine in an animal model of anxiety/depression.</a> Neuron. 62 (4), 479-493 (2009).</li><li>Yalcin, I., 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=A+time-dependent+history+of+mood+disorders+in+a+murine+model+of+neuropathic+pain.">A time-dependent history of mood disorders in a murine model of neuropathic pain.</a> Biological Psychiatry. 70 (10), 946-953 (2011).</li><li>Madathil, S. K., 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=Astrocyte-specific+overexpression+of+insulin-like+growth+factor-1+protects+hippocampal+neurons+and+reduces+behavioral+deficits+following+traumatic+brain+injury+in+mice.">Astrocyte-specific overexpression of insulin-like growth factor-1 protects hippocampal neurons and reduces behavioral deficits following traumatic brain injury in mice.</a> PloS One. 8 (6), e67204 (2013).</li><li>Sugimoto, H., Kawakami, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Low-cost+protocol+of+footprint+analysis+and+hanging+box+test+for+mice+applied+the+chronic+restraint+stress.">Low-cost protocol of footprint analysis and hanging box test for mice applied the chronic restraint stress.</a> Journal of Visualized Experiments: JoVE. (143), e59027 (2019).</li><li>Hassan, S., 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=Identifying+chronic+low+back+pain+phenotypic+domains+and+characteristics+accounting+for+individual+variation:+a+systematic+review.">Identifying chronic low back pain phenotypic domains and characteristics accounting for individual variation: a systematic review.</a> Pain. , (2023).</li></ol>

The authors declare no competing financial interests. KNW acknowledges unpaid consultation with NeuroChronix, Bessor Pharma, and USA Elixeria BioPharm, Inc.

This model of chronic back pain is simple to induce, and hypersensitivity established within 1 week can last for up to (and possibly beyond) 8 weeks. This allows for accurate study of the chronic pain state as opposed to other acute models that only last for a week or two. While we show the model in mice, the uPA-induced CBP model can also be established in rats2. An advantage of the model is that the prolonged time course provokes the development of anxiety- and depression-like behaviors, which are observed in patients with chronic lower back pain. Given the prevalence of back pain16, the ability to be performed in the more commonly used mouse models in molecular pain research is an advantage.
This induction of a pain model using uPA has been done similarly with an intraarticular injection to induce osteoarthritis3, but the method shown here (intraligament) can be done quicker and with far less risk of damage to the mouse. There is no suturing needed, and no risk of bleedout due to puncturing of the articular cavity. As it is a single injection with little preparatory work, it is also easy to blind technicians to groups for more accurate results.
The main limitation of this model involves the proper acclimation of the mice to the von Frey testing; in fact, it is recommended that mice be acclimated to their cubicle and the filaments at least a week prior to model induction to ensure that the flinch response is not due to the novelty of the environment they are in or due to seeing something moving beneath their feet.
It is critical that the injection be made into the ligaments to ensure maximal response to the urokinase and not into the muscle which produces about half the response. As the injection is close to the spine, it is still important to monitor all mice daily following injection for at least 1 week to ensure there are no complications from the procedure. If any mouse shows signs of lethargy, weight loss, paralysis, abnormal behavior, or excessive grooming of the injection site, consider removing the mouse from the study.
Future studies will examine the dorsal root ganglia (DRG) with in vitro patch clamp recordings. Flow analysis will determine the neuroimmune response and the presence of invading inflammatory cells in the DRG.

Low back pain is one of the most common causes of disability with 1 in 5 people suffering worldwide1. In spite of these efforts, few reliable animal models of back pain are popularly used in animal research in the pain field, especially in mice. Previous models have almost exclusively made use of rats for the induction of chronic back pain (CBP) such as those induced by injection of urinary plasminogen activator (uPA) into the lumbar facet joint2,3, injection of nerve growth factor (NGF) into trunk musculature4, or monosodium iodoacetate (MIA)5 or interleukin-1beta6 injection in the intravertebral disc. Of course, rats are preferred for these models mainly due to their larger size and ease of access for injection of inflammatory agents.
To be clear, mouse models of back pain do exist such as the SPARC-null mouse model of intervertebral-disc degeneration used for many years7, but these are more costly and time-consuming to establish than injection-based models. A recent mouse study established a model of lower back pain by combining NGF injection into low back muscles with vertical chronic restraint stress8. In the following protocol, we have adapted the uPA-induced CBP model from rats for mice2. Hypersensitivity is established within 1 week and persists up to 6-8 weeks. In addition, we establish that mice develop anxiety- and depression-like behaviors. Given the prevalence of back pain and the more common use of mice in molecular pain research, this durable model is readily established for use in the development of new treatment strategies for back pain relief.

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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.

Nociceptive-related behavioral testing and data analysis 
Evoked measures 
Hypersensitivity on the footpad develops within a day of urokinase injection. Within 1 week, the withdrawal threshold is significantly decreased and persists until euthanasia; this is shown through postsurgical week 4 (Figure 4A). Paw withdrawal latency is analyzed using the von Frey up-down method9 and the Hargreaves test. In the example plotted, mice with CBP (n = 4 males, 4 females) showed significantly increased mechanical sensitivity compared to controls (n = 2 males, 2 females). The model dissipates in weeks 6-7. This time course allows the evaluation of compounds to attenuate hypersensitivity at chronic time points, equivalent to years of pain experience in clinical patients. The reflexive von Frey test can be repeated several times in a single day when the efficacy of a short-lasting compound is being determined.
von Frey mechanical sensitivity test 
The sensitivity of the footpad, and thus, the severity of the back pain model is quantified by the number of withdrawal events from graded von Frey filaments with defined tensile strength. Stimulation with the lowest fiber (0.008 g, 1.65) is usually not detectable except in severe cases of allodynia; the largest fiber (6.0 g, 4.74) is about the size of a blunt paper clip end, and though it can be felt by a mouse, a na&#239;ve mouse will usually not flinch upon application. Animals are free to voluntarily move their foot away from the stimulus. The mean occurrence of withdrawal events is expressed as the number of responses out of five, with zero indicating no withdrawal, and five indicating the maximum number of withdrawals. Responses to lower fibers compared to controls indicate increased sensitivity. After induction of this model, statistically significant mechanical hypersensitivity develops within a week and persists for multiple weeks post injection (Figure 4A).
Hargreaves thermal sensitivity threshold test 
Withdrawal of the foot in seconds after exposure to the IR-induced heat stimulus is compared between (among) groups. A decrease in the withdrawal latency in seconds indicates heat hypersensitivity (Figure 4B). Animals are free to voluntarily move their foot away from the stimulus.
Cold probe thermal hypersensitivity 
The back pain model induces cold hypersensitivity on the footpad. Animals are free to voluntarily move their foot away from the stimulus. A decrease in the withdrawal latency in seconds indicates cold hypersensitivity (Figure 4C). Withdrawal latency was taken with a stopwatch from when the cold stimulus was applied to the mouse exhibiting a withdrawal behavior, licking, flicking, or repeated lifting of the affected hind paw.
Non-evoked spontaneous pain measures
<img alt="Figure 5" class="xfigimg" src="/files/ftp_upload/63997/63997fig05.jpg" /> 
Figure 5: Altered non-evoked behavioral measures. (A)&#160;Anxiety in CBP model. Total time spent in the light chamber of the light/dark box and number of rearing events are significantly lower in mice with CBP, indicating anxiety. One-way ANOVA (Dunnett&#39;s multiple comparisons test) was performed on these data: (n = 4 CBP, n = 6 Naive). Tukey post-hoc test was performed to confirm differences between specific group means. * p &#60; 0.05, ** p &#60; 0.01. (B)&#160;Depression in CBP model. The total time spent grooming and the number of times groomed during the sucrose splash test are significantly lower in mice with CBP, whereas the amount of time before grooming starts was significantly increased. One-way ANOVA (Dunnett&#39;s multiple comparisons test) was performed on these data: (n = 4 CBP, n = 6 Naive). Tukey post-hoc test was performed to confirm differences between specific group means. * p &#60; 0.05, *** p &#60; 0.001. (C) Stride alterations in mice with CBP model.&#160;Stride length between mice with CBP and na&#239;ve mice was significantly different. One-way ANOVA (Dunnett&#39;s multiple comparisons test) was performed on these data: n = 4 per group. Tukey post-hoc test was performed to confirm differences between specific group means. ** p &#60; 0.01. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/63997/63997fig05large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
Light/dark test 
A standard light/dark chamber can be used for anxiety analysis10. Mice with the back pain model are significantly less likely to spend time in the light chamber and have fewer rearing behaviors, which is indicative of the anxiety and the severity of the model. Alternatively, the elevated zero or plus mazes can be used to measure anxiety-like behaviors. Rodents with a pain model displaying anxiety-like behavior enter and spend less time in the open quadrants than na&#239;ve control animals (Figure 5A).
Depression-like behavior 
The sucrose splash test can be utilized to assess depression-like behavior in the back pain model11. The test assesses the absence of grooming behavior as a sign of depression resulting from the induced pain model12,13. Mice with back pain groom significantly fewer times and for less time overall, as well as take longer to begin grooming (latency to groom) (Figure 5B).
Mobility motor behavior 
Finally, the inkblot test can be used to differentiate gait differences between the model and control mice15. Mice with back pain show significantly shorter and wider strides compared to controls (Figure 5C). Measure the stride length for group comparisons, noting the differences in stride appearance.

Watch this Scientific Journal Video about Urokinase-type Plasminogen Activator-induced Mouse Back Pain Model at JoVE.com

Urokinase-type Plasminogen Activator-induced Mouse Back Pain Model

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 ...

urokinase-type-plasminogen-activator-induced-mouse-back-pain-model

Nanyang Technological University

Research

JoVE Journal

Behavior

865 Views.  University of New Mexico Health Sciences Center. Methods for simple, rapid induction of a back pain model in mice are provided here using an intraligament injection of urinary plasminogen activator.

Video: Urokinase-type Plasminogen Activator-induced Mouse Back Pain Model

Use of the Operant Orofacial Pain Assessment Device (OPAD) to Measure Changes in Nociceptive Behavior

We present an operant system for the detection of pain in awake, conscious rodents. The Orofacial Pain Assessment Device (OPAD) assesses pain behaviors in a more clinically relevant way by not relying on reflex-based measures of nociception. Food fasted, hairless (or shaved) rodents are placed into a Plexiglas chamber which has two Peltier-based thermodes that can be programmed to any temperature between 7 &deg;C and 60 &deg;C. The rodent is trained to make contact with these in order to access a reward bottle. During a session, a number of behavioral pain outcomes are automatically recorded and saved. These measures include the number of reward bottle activations (licks) and facial contact stimuli (face contacts), but custom measures like the lick/face ratio (total number of licks per session/total number of contacts) can also be created. The stimulus temperature can be set to a single temperature or multiple temperatures within a session. The OPAD is a high-throughput, easy to use operant assay which will lead to better translation of pain research in the future as it includes cortical input instead of relying on spinal reflex-based nociceptive assays.

Use of the Operant Orofacial Pain Assessment Device OPAD to Measure Changes in Nociceptive Behavior

We present a user-friendly, high-throughput operant system for the evaluation of pain behaviors in awake, conscious rodents. The Orofacial Pain Assessment Device (OPAD) can assess pain through a reward/conflict paradigm thus providing a more humane way of testing. This protocol will yield more clinically relevant and translational data from rodents.

We present an operant  system for the detection of pain in awake, conscious rodents. The Orofacial  Pain Assessment Device (OPAD) assesses pain behaviors ...

Assessing Functional Performance in the Mdx Mouse Model

Duchenne muscular dystrophy (DMD) is a severe and progressive muscle wasting disorder for which no cure is available. Nevertheless, several potential pharmaceutical compounds and gene therapy approaches have progressed into clinical trials. With improvement in muscle function being the most important end point in these trials, a lot of emphasis has been placed on setting up reliable, reproducible, and easy to perform functional tests to pre clinically assess muscle function, strength, condition, and coordination in the mdx mouse model for DMD. Both invasive and noninvasive tests are available. Tests that do not exacerbate the disease can be used to determine the natural history of the disease and the effects of therapeutic interventions (e.g. forelimb grip strength test, two different hanging tests using either a wire or a grid and rotarod running). Alternatively, forced treadmill running can be used to enhance disease progression and/or assess protective effects of therapeutic interventions on disease pathology. We here describe how to perform these most commonly used functional tests in a reliable and reproducible manner. Using these protocols based on standard operating procedures enables comparison of data between different laboratories.

Assessing Functional Performance in the Mdx Mouse Model

The primary outcome measure in clinical trials for neuromuscular disorders is generally improved muscle function. Therefore, assessing the effect of potential therapeutic compounds on muscle performance pre clinically in mouse models is of great importance. We here describe several functional tests to address this.

Duchenne muscular dystrophy (DMD) is a severe and progressive muscle wasting disorder for which no cure is available. Nevertheless, several potential ...

Determining Pain Detection and Tolerance Thresholds Using an Integrated, Multi-Modal Pain Task Battery

Human pain models are useful in the assessing the analgesic effect of drugs, providing information about a drug&#39;s pharmacology and identify potentially suitable therapeutic populations. The need to use a comprehensive battery of pain models is highlighted by studies whereby only a single pain model, thought to relate to the clinical situation, demonstrates lack of efficacy. No single experimental model can mimic the complex nature of clinical pain. The integrated, multi-modal pain task&#160;battery presented here encompasses the electrical stimulation task, pressure stimulation task, cold pressor task, the UVB inflammatory model which includes a thermal task and a paradigm for inhibitory conditioned pain modulation. These human pain models have been tested for predicative validity and reliability both in their own right and in combination, and can be used repeatedly, quickly, in short succession, with minimum burden for the subject and with a modest quantity of equipment. This allows a drug to be fully characterized and profiled for analgesic effect which is especially useful for drugs with a novel or untested mechanism of action.

Human pain models are valuable tools used to assess the analgesic potential of novel compounds and predict their clinical efficacy, especially when used in an integrated manner. Although implementation of these models is complex, with proper execution, the pain models described in this protocol can provide predictive and reliable results.

Human pain models are useful in the assessing the analgesic effect of drugs, providing information about a drug&#39;s pharmacology and identify ...

A Protocol of Manual Tests to Measure Sensation and Pain in Humans

Numerous qualitative and quantitative techniques can be used to test sensory nerves and pain in both research and clinical settings. The current study demonstrates a quantitative sensory testing protocol using techniques to measure tactile sensation and pain threshold for pressure and heat using portable and easily accessed equipment. These techniques and equipment are ideal for new laboratories and clinics where cost is a concern or a limiting factor. We demonstrate measurement techniques for the following: cutaneous mechanical sensitivity on the arms and legs (von-Frey filaments), radiant and contact heat sensitivity (with both threshold and qualitative assessments using the Visual Analog Scale (VAS)), and mechanical pressure sensitivity (algometer, with both threshold and the VAS). The techniques and equipment described and demonstrated here can be easily purchased, stored, and transported by most clinics and research laboratories around the world. A limitation of this approach is a lack of automation or computer control. Thus, these processes can be more labor intensive in terms of personnel training and data recording than the more sophisticated equipment. We provide a set of reliability data for the demonstrated techniques. From our description, a new laboratory should be able to set up and run these tests and to develop their own internal reliability data.

The goal of this procedure is to demonstrate a battery of quantitative techniques for sensory and pain measurement in humans. The equipment and techniques described are commonly found in pain clinics or are easy to obtain.

Numerous qualitative and quantitative techniques can be used to test sensory nerves and pain in both research and clinical settings. The current study ...

Psychophysically-anchored, Robust Thresholding in Studying Pain-related Lateralization of Oscillatory Prestimulus Activity

In perceptual studies, it is often important to objectively assess the equality of delivered stimulation across participants or to quantify the intra-individual sensation magnitude that is evoked by stimulation over multiple trials. This requires a robust mapping of stimulus magnitude to perceived intensity and is commonly achieved by psychophysical estimation methods such as the staircase procedure. Newer, more efficient procedures like the QUEST algorithm fit a psychophysical function to the data in real time while at the same time maximizing the efficiency of data collection. A robust estimate of the threshold intensity between painful and nonpainful perceptions can then be used to reduce the influence of variations in sensory input in subsequent analyses of oscillatory brain activity. By stimulating at a constant threshold intensity determined by an adaptive estimation procedure, the variance in the ratings can be directly attributed to perceptual processes. Oscillatory activity can then be contrasted between &#34;pain&#34; and &#34;no-pain&#34; trials directly, yielding activity that closely relates to perceptual classification processes in nociception.

Psychophysical methods such as the QUEST estimation procedure can efficiently yield robust estimates of the stimulation intensity at which nonpainful sensations transition into painful sensations. By stimulating repeatedly at the threshold intensity, the variability in rating responses can directly be attributed to perceptual classifications in subsequent analyses.

In perceptual studies, it is often important to objectively assess the equality of delivered stimulation across participants or to quantify the ...

Treating Low Back Pain in Failed Back Surgery Patients with Multicolumn-lead Spinal Cord Stimulation

Failed back surgery syndrome (FBSS) refers to persistent, chronic pain following spinal surgery. Spinal cord stimulation with dorsal epidural leads can be used to treat back and leg pain in FBSS patients. This paper presents a detailed protocol for using spinal cord stimulation with surgical leads in FBSS patients. In our department, with the patient under general anesthesia, we place the lead in the epidural space by means of a small laminectomy at the 10th thoracic level. Placement of the lead is followed by a 1 month trial period with an externalized lead. If pain relief is greater than 50% at the end of this 1 month stimulation trial (required by Belgian reimbursement criteria), an internal pulse generator is then placed under the skin and connected to the lead in a second surgical procedure. We have demonstrated that using this technique in rigorously selected FBSS patients can significantly improve back pain, leg pain, patient activity, and quality of life for a sustained period of time.

This paper presents a method that uses spinal cord stimulation with a multicolumn lead to treat neuropathic low back pain in failed back surgery patients.

Failed back surgery syndrome (FBSS) refers to persistent, chronic pain following spinal surgery. Spinal cord stimulation with dorsal epidural leads can be ...

Measuring Active and Passive Tameness Separately in Mice

Domesticated animals such as dogs and laboratory mice show a high level of tameness, which is important for humans to handle them easily. Tameness has two behavioral components: a reluctance to avoid humans (passive tameness) and a motivation to approach humans (active tameness). To quantify these components in mice, we previously developed behavioral tests for active tameness, passive tameness, and the willingness to stay on a human hand, each designed to be completed within 3 min. The data obtained were used for selective breeding, with a large number of mice analyzed per generation. The active tameness test measures the movement of the mouse toward a human hand and the contact it engages in. The passive tameness test measures the duration of time that a mouse tolerates human touch. In the stay-on-hand test, a mouse is placed on a human hand and touched slowly using the thumb of that hand; the duration of time that the animal remains on the hand is measured. Here, we describe the test set-up and apparatus, explain the procedures, and discuss the appropriate data analysis. Finally, we explain how to interpret the results.

Tameness in animals includes a reduction of avoidance responses to humans (passive tameness) and an increase in active approaches to humans (active tameness). Here, we describe detailed protocols for three behavioral tests (active tameness, passive tameness, and stay-on-hand tests) to separately measure the active and passive tameness of mice.

Domesticated animals such as dogs and laboratory mice show a high level of tameness, which is important for humans to handle them easily. Tameness has two ...

Simultaneous Recordings of Cortical Local Field Potentials and Electrocorticograms in Response to Nociceptive Laser Stimuli from Freely Moving Rats

Electrocortical responses, elicited by laser heat pulses that selectively activate nociceptive free nerve endings, are widely used in many animal and human studies to investigate the cortical processing of nociceptive information. These laser-evoked brain potentials (LEPs) consist of several transient responses that are time-locked to the onset of laser stimuli. However, the functional properties of the LEP responses are still largely unknown, due to the lack of a sampling technique that can simultaneously record neural activities at the surface of the cortex (i.e., electrocorticogram [ECoG] and scalp electroencephalogram [scalp EEG]) and inside the brain (i.e., local field potential [LFP]). To address this issue, we present here an animal protocol using freely moving rats. This protocol is composed of three main procedures: (1) animal preparation and surgical procedures, (2) a simultaneous recording of ECoG and LFP in response to nociceptive laser stimuli, and (3) data analysis and feature extraction. Specifically, with the help of a 3D-printed protective shell, both ECoG and LFP electrodes implanted on the rat&#39;s skull were securely held together. During data collection, laser pulses were delivered on the rat&#39;s forepaws through gaps in the bottom of the chamber when the animal was in spontaneous stillness. Ongoing white noise was played to avoid the activation of the auditory system by the laser-generated ultrasounds. As a consequence, only nociceptive responses were selectively recorded. Using the standard analytical procedures (e.g., band-pass filtering, epoch extraction, and baseline correction) to extract stimulus-related brain responses, we obtained results showing that LEPs with a high signal-to-noise ratio were simultaneously recorded from ECoG and LFP electrodes. This methodology makes the simultaneous recording of ECoG and LFP activities possible, which provides a bridge of electrocortical signals at the mesoscopic and macroscopic levels, thereby facilitating the investigation of nociceptive information processing in the brain.

We developed a technique that simultaneously records both electrocorticography and local field potentials in response to nociceptive laser stimuli from freely moving rats. This technique helps establish a direct relationship of electrocortical signals at the mesoscopic and macroscopic levels, which facilitates the investigation of nociceptive information processing in the brain.

Electrocortical responses, elicited by laser heat pulses that selectively activate nociceptive free nerve endings, are widely used in many animal and ...

Multi-Modal Signals for Analyzing Pain Responses to Thermal and Electrical Stimuli

The assessment of pain relies mostly on methods that require a person to communicate. However, for people with cognitive and verbal impairments, existing methods are not sufficient as they lack reliability and validity. To approach this problem, recent research focuses on an objective pain assessment facilitated by parameters of responses derived from physiology, and video and audio signals. To develop reliable automated pain recognition systems, efforts have been made in creating multimodal databases in order to analyze pain and detect valid pain patterns. While the results are promising, they only focus on discriminating pain or pain intensities versus no pain. In order to advance this, research should also consider the quality and duration of pain as they provide additional valuable information for more advanced pain management. To complement existing databases and the analysis of pain regarding quality and length, this paper proposes a psychophysiological experiment to elicit, measure, and collect valid pain reactions. Participants are subjected to painful stimuli that differ in intensity (low, medium, and high), duration (5 s / 1 min), and modality (heat / electric pain) while audio, video (e.g., facial expressions, body gestures, facial skin temperature), and physiological signals (e.g., electrocardiogram [ECG], skin conductance level [SCL], facial electromyography [EMG], and EMG of M. trapezius) are being recorded. The study consists of a calibration phase to determine a subject&#8217;s individual pain range (from low to intolerable pain) and a stimulation phase in which pain stimuli, depending on the calibrated range, are applied. The obtained data may allow refining, improving, and evaluating automated recognition systems in terms of an objective pain assessment. For further development of such systems and to investigate pain reactions in more detail, additional pain modalities such as pressure, chemical, or cold pain should be included in future studies. Recorded data of this study will be released as the &#8220;X-ITE Pain Database&#8221;.

This article focuses on the experimental elicitation of pain through heat (thermal) and electrical stimulation while recording physiological, visual, and paralinguistic responses. It aims at collecting valid multimodal data for analyzing pain based on its intensity, quality, and duration.&#160;

The assessment of pain relies mostly on methods that require a person to communicate. However, for people with cognitive and verbal impairments, existing ...

Chronic Post-Ischemia Pain Model for Complex Regional Pain Syndrome Type-I in Rats

Complex regional pain syndrome type-I (CRPS-I) is a neurological disease that causes severe pain among patients and remains an unresolved medical condition. However, the underlying mechanisms of CRPS-I have yet to be revealed. It is known that ischemia/reperfusion is one of the leading factors that causes CRPS-I. By means of prolonged ischemia and reperfusion of the hind limb, the rat chronic post-ischemia pain (CPIP) model has been established to mimic CRPS-I. The CPIP model has become a well-recognized animal model for studying the mechanisms of CRPS-I. This protocol describes the detailed procedures involved in the establishment of the rat model of CPIP, including anesthesia, followed by ischemia/reperfusion of the hind limb. Characteristics of the rat CPIP model are further evaluated by measuring the mechanical and thermal hypersensitivities of the hind limb as well as the nocifensive responses to acute capsaicin injection. The rat CPIP model exhibits several CRPS-I-like manifestations, including hind limb edema and hyperemia in the early stage after establishment, persistent thermal and mechanical hypersensitivities, and increased nocifensive responses to acute capsaicin injection. These characteristics render it a suitable animal model for further investigation of the mechanisms involved in CRPS-I.

Provided here is a protocol that details steps to establish an animal model of chronic post-ischemia pain (CPIP). This is a well-recognized model mimicking human complex regional pain syndrome type-I. Mechanical and thermal hypersensitivities are further evaluated, as well as capsaicin-induced nocifensive behaviors observed in the CPIP rat model.

Urokinase-type Plasminogen Activator-induced Mouse Back Pain Model

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Determining Pain Detection and Tolerance Thresholds Using an Integrated, Multi-Modal Pain Task Battery

A Protocol of Manual Tests to Measure Sensation and Pain in Humans

Psychophysically-anchored, Robust Thresholding in Studying Pain-related Lateralization of Oscillatory Prestimulus Activity

Treating Low Back Pain in Failed Back Surgery Patients with Multicolumn-lead Spinal Cord Stimulation

Measuring Active and Passive Tameness Separately in Mice

Simultaneous Recordings of Cortical Local Field Potentials and Electrocorticograms in Response to Nociceptive Laser Stimuli from Freely Moving Rats

Multi-Modal Signals for Analyzing Pain Responses to Thermal and Electrical Stimuli

Chronic Post-Ischemia Pain Model for Complex Regional Pain Syndrome Type-I in Rats