Multiparametric magnetic resonance imaging for detection of pathological changes in the central nervous system of a mouse model of multiple sclerosis in vivo.

Multiple sclerosis (MS) is an autoimmune disease involving demyelination and axonal damage in the central nervous system (CNS). In this study, we investigated pathological changes in the lumbar spinal cord of C57BL/6 mice induced with progressive experimental autoimmune encephalomyelitis (EAE) disease using 9.4-T magnetic resonance imaging (MRI). Multiparametric MRI measurements including MR spectroscopy, diffusion tensor imaging (DTI) and volumetric analyses were applied to detect metabolic changes in the CNS of EAE mice. Compared with healthy mice, EAE mice showed a significant reduction in N-acetyl aspartate and increases in choline, glycine, taurine and lactate. DTI revealed a significant reduction in fractional anisotropy and axial diffusivity and an increase in radial diffusivity in the lumbar spinal cord white matter (WM), while in the grey matter (GM), fractional anisotropy increased. High-resolution structural imaging also revealed lumbar spinal cord WM hypertrophy and GM atrophy. Importantly, these MRI changes were strongly correlated with EAE disease scoring and pathological changes in the lumbar (L2-L6), particularly WM demyelination lesions and aggregation of immune cells (microglia/macrophages and astrocytes) in this region. This study identified changes in MRI biomarker signatures that can be useful for evaluating the efficacy of novel drugs using EAE models in vivo.

ß-Glucan receptors on IL-4 activated macrophages are required for hookworm larvae recognition and trapping.

Recent advances in the field of host immunity against parasitic nematodes have revealed the importance of macrophages in trapping tissue migratory larvae. Protective immune mechanisms against the rodent hookworm Nippostrongylus brasiliensis (Nb) are mediated, at least in part, by IL-4-activated macrophages that bind and trap larvae in the lung. However, it is still not clear how host macrophages recognize the parasite. An in vitro co-culture system of bone marrow-derived macrophages and Nb infective larvae was utilized to screen for the possible ligand-receptor pair involved in macrophage attack of larvae. Competitive binding assays revealed an important role for ß-glucan recognition in the process. We further identified a role for CD11b and the non-classical pattern recognition receptor ephrin-A2 (EphA2), but not the highly expressed ß-glucan dectin-1 receptor, in this process of recognition. This work raises the possibility that parasitic nematodes synthesize ß-glucans and it identifies CD11b and ephrin-A2 as important pattern recognition receptors involved in the host recognition of these evolutionary old pathogens. To our knowledge, this is the first time that EphA2 has been implicated in immune responses to a helminth.

Design, synthesis and evaluation of alpha lipoic acid derivatives to treat multiple sclerosis-associated central neuropathic pain.

Multiple sclerosis-associated central neuropathic pain (MS-CNP) is difficult to alleviate with clinically used pain-killers and so there is a large unmet medical need for novel treatments for alleviating MS-CNP. Although (R)-alpha lipoic acid (ALA) evoked significant pain relief efficacy in a mouse model of multiple sclerosis-associated central neuropathic pain (MS-CNP), this dietary supplement has poor oral bioavailability due to low gastric stability. Eight ester prodrugs of the R enantiomer of ALA [(R)-ALA] were designed encompassing a range of biocompatible hydrophobic and hydrophilic features and synthesized in an effort to identify a prodrug candidate that was stable at gastric and upper gastrointestinal tract (GIT) pH, and that could be released (hydrolyzed by esterases) in the blood to (R)-ALA immediately after absorption into the portal vein (i.e., highly desirable features for pain relief development). These biocompatible hydrophobic and hydrophilic (R)-ALA pro-dugs underwent comprehensive preliminary screening to reveal PD-ALA4 HCl salt (10) as a promising candidate and PD-ALA 7 (8) could be a viable substitute, utilizing enzyme-free gastric and intestinal stability assessments, LogP evaluations, in vitro plasma stability and caco-2 cell monolayer permeability.

Characterisation of a rat model of mechanical low back pain at an advanced stage using immunohistochemical methods.

Chronic low back pain (LBP) has high prevalence in the adult population which is associated with enormous disability. Hence, our aim was to further characterise our LBP rat model by using immunohistological and immunohistochemical methods at an advanced stage (day 49) of the model. Male Sprague-Dawley rats were anaesthetised and their lumbar L4/L5 and L5/L6 intervertebral discs (IVDs) were punctured (0.5 mm outer diameter, 2 mm-deep) 10 times per disc. Sham-rats underwent similar surgery, but no discs were punctured. For LBP- but not sham-rats, noxious pressure hyperalgesia was fully developed in the lumbar axial deep tissues on day 21 post-surgery, which was maintained until at least day 49. In the lumbar (L4-L6) dorsal root ganglia (DRGs), somatostatin (SRIF) and the somatostatin receptor type 4 (SST4 receptor) were co-localised with substance P and IB4, markers of small diameter unmyelinated peptidergic and non-peptidergic C-fibres respectively as well as with NF200, a marker of medium to large diameter neurons. On day 49, there was increased expression of SRIF but not the somatostatin receptor type 4 (SST4 receptor) in the lumbar DRGs and the spinal dorsal horns. There were increased DRG expression levels of the putative pro-nociceptive mediators: phosphorylated p38 (pp38) mitogen-activated protein kinase (MAPK) and phosphorylated p44/p42 MAPK (pp44/pp42 MAPK) as well as pp38 MAPK expression levels in the lumbar spinal cord. Taken together, the increased expression of SRIF in the lumbar DRGs and spinal cord and its co-localisation with nociceptive fibres in DRG sections suggest a potential role of SRIF in modulating chronic mechanical LBP.

Comparative studies of glial fibrillary acidic protein and brain-derived neurotrophic factor expression in two transgenic mouse models of Alzheimer's disease.

In Alzheimer's disease (AD) glial fibrillary acidic protein (GFAP) is expressed by reactive astrocytes surrounding ß-amyloid (Aß) plaques, whereas brain-derived neurotrophic factor (BDNF) levels are typically reduced. We compared the expression of GFAP, BDNF, and its precursor proBDNF in the dorsal hippocampus of two transgenic AD mouse models. APPSwe YAC mice expressing the APPSwe transgene on a yeast artificial chromosome (YAC) were assessed at age 4 and 21 months, and APPSwe/PS1dE9 mice co-expressing mutant amyloid precursor protein (APPSwe) and presenilin-1 (PS1dE9) were assessed at age 4 and 9 months. Significantly increased (1.4-fold) GFAP expression was observed in APPSwe YAC c.f. wild-type (Wt) mice aged 21 months, when Aß deposition was first evident in these mice. In APPSwe/PS1dE9 mice aged 4 and 9 months, GFAP expression was significantly increased (1.6- and 3.1-fold, respectively) c.f. Wt mice, and was associated with robust Aß deposition at 9 months. BDNF expression was significantly lower in 4- and 21-month old APPSwe YAC mice (0.8- and 0.6-fold, respectively) c.f. age-matched Wt mice, whereas proBDNF expression was significantly higher (10-fold) in the APPSwe YAC c.f. Wt mice aged 21 months. In APPSwe/PS1dE9 mice aged 4 months, BDNF expression was significantly lower (0.4-fold) c.f. age-matched Wt mice and was equivalent to that in 9-month old mice of both genotypes; proBDNF expression mirrored that of BDNF in this strain. These findings support a role for reactive astrocytes and neuroinflammation, rather than BDNF, in the spatial memory deficits previously reported for APPSwe YAC and APPSwe/PS1dE9 mice.

Pharmacological inhibition of the NLRP3 inflammasome as a potential target for multiple sclerosis induced central neuropathic pain.

The NOD-like receptor (NLR) family pyrin domain-containing protein 3 (NLRP3) inflammasome is implicated in the pathogenesis of multiple diseases including neuroinflammation associated with multiple sclerosis (MS). However, the extent to which NLRP3 has a pathobiological role in MS-associated central neuropathic pain (CNP) is unknown. Hence, the present study was designed to address this issue using an optimised relapsing-remitting experimental encephalomyelitis (RR-EAE)-mouse model of MS-associated neuropathic pain. RR-EAE mice with fully developed mechanical allodynia in the bilateral hindpaws (paw withdrawal thresholds (PWTs) ≤ 1 g) at day 16 post-immunisation (p.i.) were administered single oral bolus doses of MCC950, a selective and potent small-molecule inhibitor of NLRP3, once daily for 21 consecutive days. Following administration of the first dose of MCC950 at 50 mg kg-1, the mean (± SEM) peak anti-allodynic effect was observed at ~ 1 h post-dosing with a duration of action of ~ 2 h. Following chronic dosing with MCC950, mechanical allodynia in the bilateral hindpaws was progressively reversed by oral treatment with MCC950 (50 mg kg-1 day-1), but not vehicle. Specifically, by day 25 p.i. and continuing until study completion on day 36 p.i., bilateral hindpaw PWTs of RR-EAE mice treated with MCC950 (50 mg kg-1 day-1) did not differ significantly (P > 0.05) from the corresponding hindpaw PWTs for the sham (control) group. In addition, MCC950 at 50 mg kg-1 day-1 attenuated disease relapses in RR-EAE mice indicated by tail limpness as well as hindlimb weakness. Together, our findings suggest that inhibition of NLRP3 inflammasome activation may be a potential therapeutic approach to alleviate MS-associated CNP and disease relapses in patients with RR-MS.

Neurotrophins and Neuropathic Pain: Role in Pathobiology.

Neurotrophins (NTs) belong to a family of trophic factors that regulate the survival, growth and programmed cell death of neurons. In mammals, there are four structurally and functionally related NT proteins, viz. nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), neurotrophin 3 and neurotrophin 4. Most research on NTs to date has focussed on the effects of NGF and BDNF signalling via their respective cognate high affinity neurotrophic tyrosine kinase viz TrkA and TrkB receptors. Apart from the key physiologic roles of NGF and BDNF in peripheral and central nervous system function, NGF and BDNF signalling via TrkA and TrkB receptors respectively have been implicated in mechanisms underpinning neuropathic pain. Additionally, NGF and BDNF signalling via the low-affinity pan neurotrophin receptor at 75 kDa (p75NTR) may also contribute to the pathobiology of neuropathic pain. In this review, we critically assess the role of neurotrophins signalling via their cognate high affinity receptors as well as the low affinity p75NTR in the pathophysiology of peripheral neuropathic and central neuropathic pain. We also identify knowledge gaps to guide future research aimed at generating novel insight on how to optimally modulate NT signalling for discovery of novel therapeutics to improve neuropathic pain relief.

Multiple sclerosis-induced neuropathic pain: pharmacological management and pathophysiological insights from rodent EAE models.

In patients with multiple sclerosis (MS), pain is a frequent and disabling symptom. The prevalence is in the range 29-86 % depending upon the assessment protocols utilised and the definition of pain applied. Neuropathic pain that develops secondary to demyelination, neuroinflammation and axonal damage in the central nervous system is the most distressing and difficult type of pain to treat. Although dysaesthetic extremity pain, L'hermitte's sign and trigeminal neuralgia are the most common neuropathic pain conditions reported by patients with MS, research directed at gaining insight into the complex mechanisms underpinning the pathobiology of MS-associated neuropathic pain is in its relative infancy. By contrast, there is a wealth of knowledge on the neurobiology of neuropathic pain induced by peripheral nerve injury. To date, the majority of research in the MS field has used rodent models of experimental autoimmune encephalomyelitis (EAE) as these models have many clinical and neuropathological features in common with those observed in patients with MS. However, it is only relatively recently that EAE-rodents have been utilised to investigate the mechanisms contributing to the development and maintenance of MS-associated central neuropathic pain. Importantly, EAE-rodent models exhibit pro-nociceptive behaviours predominantly in the lower extremities (tail and hindlimbs) as seen clinically in patients with MS-neuropathic pain. Herein, we review research to date on the pathophysiological mechanisms underpinning MS-associated neuropathic pain as well as the pharmacological management of this condition. We also identify knowledge gaps to guide future research in this important field.

Inhibiting Eph/ephrin signaling reduces vascular leak and endothelial cell dysfunction in mice with sepsis.

Sepsis is a life-threatening disease caused by a dysregulated host response to infection, resulting in 11 million deaths globally each year. Vascular endothelial cell dysfunction results in the loss of endothelial barrier integrity, which contributes to sepsis-induced multiple organ failure and mortality. Erythropoietin-producing hepatocellular carcinoma (Eph) receptors and their ephrin ligands play a key role in vascular endothelial barrier disruption but are currently not a therapeutic target in sepsis. Using a cecal ligation and puncture (CLP) mouse model of sepsis, we showed that prophylactic or therapeutic treatment of mice with EphA4-Fc, a decoy receptor and pan-ephrin inhibitor, resulted in improved survival and a reduction in vascular leak, lung injury, and endothelial cell dysfunction. EphA2-/- mice also exhibited reduced mortality and pathology after CLP compared with wild-type mice. Proteomics of plasma samples from mice with sepsis after CLP revealed dysregulation of a number of Eph/ephrins, including EphA2/ephrin A1. Administration of EphA4-Fc to cultured human endothelial cells pretreated with TNF-α or ephrin-A1 prevented loss of endothelial junction proteins, specifically VE-cadherin, with maintenance of endothelial barrier integrity. In children admitted to hospital with fever and suspected infection, we observed that changes in EphA2/ephrin A1 in serum samples correlated with endothelial and organ dysfunction. Targeting Eph/ephrin signaling may be a potential therapeutic strategy to reduce sepsis-induced endothelial dysfunction and mortality.

Transient binocular vision loss and pain insensitivity in Klippel-Feil syndrome: a case report.

BACKGROUND: Klippel-Feil syndrome is a rare congenital bone disorder characterized by an abnormal fusion of two or more cervical spine vertebrae. Individuals with Klippel-Feil syndrome exhibit diverse clinical manifestations, including skeletal irregularities, visual and hearing impairments, orofacial anomalies, and anomalies in various internal organs, such as the heart, kidneys, genitourinary system, and nervous system. CASE PRESENTATION: This case report describes a 12-year-old Pashtun female patient who presented with acute bilateral visual loss. The patient had Klippel-Feil syndrome, with the typical clinical triad symptoms of Klippel-Feil syndrome, along with Sprengel's deformity. She also exhibited generalized hypoalgesia, which had previously resulted in widespread burn-related injuries. Upon examination, bilateral optic disc swelling was observed, but intracranial pressure was found to be normal. Extensive investigations yielded normal results, except for hypocalcemia and low vitamin D levels, while parathyroid function remained within the normal range. Visual acuity improved following 2 months of calcium and vitamin D supplementation, suggesting that the visual loss and optic nerve swelling were attributed to hypocalcemia. Given the normal parathyroid function, it is possible that hypocalcemia resulted from low vitamin D levels, which can occur after severe burn scarring. Furthermore, the patient received a provisional diagnosis of congenital insensitivity to pain on the basis of the detailed medical history and the findings of severe and widespread loss of the ability to perceive painful stimuli, as well as impaired temperature sensation. However, due to limitations in genetic testing, confirmation of the congenital insensitivity to pain diagnosis could not be obtained. CONCLUSION: This case highlights a rare presentation of transient binocular vision loss and pain insensitivity in a patient with Klippel-Feil syndrome, emphasizing the importance of considering unusual associations in symptom interpretation.

Post-COVID Opsoclonus Myoclonus Syndrome: A Case Report From Pakistan.

Background: Coronavirus disease-2019 (COVID-19), caused by the severe acute respiratory distress syndrome-coronavirus-2 (SARS-CoV-2), is primarily a respiratory infection but has been recently associated with a variety of neurological symptoms. We present herewith a COVID-19 case manifesting as opsoclonus-myoclonus syndrome (OMS), a rare neurological disorder. Case Presentation: A 63-year-old male diagnosed with COVID-19 infection developed behavioral changes, confusion, and insomnia followed by reduced mobility and abnormal eye movements within 48 h of recovery from respiratory symptoms associated with COVID-19. On examination, he had rapid, chaotic, involuntary saccadic, multidirectional eye movements (opsoclonus), and limb myoclonus together with truncal ataxia. CSF analysis, MRI of the brain, and screening for anti-neuronal and encephalitis related antibodies were negative. Extensive testing revealed no underlying malignancy. The patient was successfully treated with intravenous immunoglobulin (IVIG) with complete resolution of symptoms within 4 weeks of treatment. Conclusion: COVID-19 infection can be associated with the manifestation of opsoclonus myoclonus syndrome, a rare neurological disorder that can be treated with IVIG if not responsive to corticosteroids.

J-2156, a somatostatin receptor type 4 agonist, alleviates mechanical hyperalgesia in a rat model of chronic low back pain.

Chronic low back pain (LBP) ranks among the most common reasons for patient visits to healthcare providers. Drug treatments often provide only partial pain relief and are associated with considerable side-effects. J-2156 [(1'S,2S)-4amino-N-(1'-carbamoyl-2'-phenylethyl)-2-(4"-methyl-1"-naphthalenesulfonylamino)butanamide] is an agonist that binds with nanomolar affinity to the rat and human somatostatin receptor type 4 (SST4 receptor). Hence, our aim was to assess the efficacy of J-2156 for relief of chronic mechanical LBP in a rat model. Male Sprague Dawley rats were anaesthetised and their lumbar L4/L5 and L5/L6 intervertebral discs (IVDs) were punctured (0.5 mm outer diameter, 2 mm-deep) 10 times per disc. Sham-rats underwent similar surgery, but without disc puncture. For LBP-rats, noxious pressure hyperalgesia developed in the lumbar axial deep tissues from day 7 to day 21 post-surgery, which was maintained until study completion. Importantly, mechanical hyperalgesia did not develop in the lumbar axial deep tissues of sham-rats. In LBP-rats, single intraperitoneal (i.p.) injection of J-2156 (3, 10, 30 mg kg-1) alleviated primary and secondary hyperalgesia in the lumbar axial deep tissues at L4/L5 and L1, respectively. This was accompanied by a reduction in the otherwise augmented lumbar (L4-L6) dorsal root ganglia expression levels of the pro-nociceptive mediators: phosphorylated p38 (pp38) mitogen-activated protein kinase (MAPK) and phosphorylated p44/p42 MAPK and a reduction in pp38 MAPK in the lumbar enlargement of the spinal cord. The SST4 receptor is worthy of further investigation as a target for discovery of novel analgesics for the relief of chronic LBP.

The Somatostatin Receptor-4 Agonist J-2156 Alleviates Mechanical Hypersensitivity in a Rat Model of Breast Cancer Induced Bone Pain.

In the majority of patients with breast cancer in the advanced stages, skeletal metastases are common, which may cause excruciating pain. Currently available drug treatments for relief of breast cancer-induced bone pain (BCIBP) include non-steroidal anti-inflammatory drugs and strong opioid analgesics along with inhibitors of osteoclast activity such as bisphosphonates and monoclonal antibodies such as denosumab. However, these medications often lack efficacy and/or they may produce serious dose-limiting side effects. In the present study, we show that J-2156, a somatostatin receptor type 4 (SST4 receptor) selective agonist, reverses pain-like behaviors in a rat model of BCIBP induced by unilateral intra-tibial injection of Walker 256 breast cancer cells. Following intraperitoneal administration, the ED50 of J-2156 for the relief of mechanical allodynia and mechanical hyperalgesia in the ipsilateral hindpaws was 3.7 and 8.0 mg/kg, respectively. Importantly, the vast majority of somatosensory neurons in the dorsal root ganglia including small diameter C-fibers and medium-large diameter fibers, that play a crucial role in cancer pain hypersensitivities, expressed the SST4 receptor. J-2156 mediated pain relief in BCIBP-rats was confirmed by observations of a reduction in the levels of phosphorylated extracellular signal-regulated kinase (pERK), a protein essential for central sensitization and persistent pain, in the spinal dorsal horn. Our results demonstrate the potential of the SST4 receptor as a pharmacological target for relief of BCIBP and we anticipate the present work to be a starting point for further mechanism-based studies.

Attenuation of the Infiltration of Angiotensin II Expressing CD3+ T-Cells and the Modulation of Nerve Growth Factor in Lumbar Dorsal Root Ganglia - A Possible Mechanism Underpinning Analgesia Produced by EMA300, An Angiotensin II Type 2 (AT2) Receptor Antagonist.

Recent preclinical and proof-of-concept clinical studies have shown promising analgesic efficacy of selective small molecule angiotensin II type 2 (AT2) receptor antagonists in the alleviation of peripheral neuropathic pain. However, their cellular and molecular mechanism of action requires further investigation. To address this issue, groups of adult male Sprague-Dawley rats with fully developed unilateral hindpaw hypersensitivity, following chronic constriction injury (CCI) of the sciatic nerve, received a single intraperitoneal bolus dose of the small molecule AT2 receptor antagonist, EMA300 (10 mg kg-1), or vehicle. At the time of peak EMA300-mediated analgesia (∼1 h post-dosing), groups of CCI-rats administered either EMA300 or vehicle were euthanized. A separate group of rats that underwent sham surgery were also included. The lumbar (L4-L6) dorsal root ganglia (DRGs) were obtained from all experimental cohorts and processed for immunohistochemistry and western blot studies. In vehicle treated CCI-rats, there was a significant increase in the expression levels of angiotensin II (Ang II), but not the AT2 receptor, in the ipsilateral lumbar DRGs. The elevated levels of Ang II in the ipsilateral lumbar DRGs of CCI-rats were at least in part contributed by CD3+ T-cells, satellite glial cells (SGCs) and subsets of neurons. Our findings suggest that the analgesic effect of EMA300 in CCI-rats involves multimodal actions that appear to be mediated at least in part by a significant reduction in the otherwise increased expression levels of Ang II as well as the number of Ang II-expressing CD3+ T-cells in the ipsilateral lumbar DRGs of CCI-rats. Additionally, the acute anti-allodynic effects of EMA300 in CCI-rats were accompanied by rescue of the otherwise decreased expression of mature nerve growth factor (NGF) in the ipsilateral lumbar DRGs of CCI-rats. In contrast, the increased expression levels of TrkA and glial fibrillary acidic protein in the ipsilateral lumbar DRGs of vehicle-treated CCI-rats were not attenuated by a single bolus dose of EMA300. Consistent with our previous findings, there was also a significant decrease in the augmented levels of the downstream mediators of Ang II/AT2 receptor signaling, i.e., phosphorylated-p38 mitogen-activated protein kinase (MAPK) and phosphorylated-p44/p42 MAPK, in the ipsilateral lumbar DRGs.

Antiallodynic effects of alpha lipoic acid in an optimized RR-EAE mouse model of MS-neuropathic pain are accompanied by attenuation of upregulated BDNF-TrkB-ERK signaling in the dorsal horn of the spinal cord.

Neuropathic pain may affect patients with multiple sclerosis (MS) even in early disease. In an experimental autoimmune encephalomyelitis (EAE)-mouse model of MS, chronic alpha lipoic acid (ALA) treatment reduced clinical disease severity, but MS-neuropathic pain was not assessed. Hence, we investigated the pain-relieving efficacy and mode of action of ALA using our optimized relapsing-remitting (RR)-EAE mouse model of MS-associated neuropathic pain. C57BL/6 mice were immunized with MOG35-55 and adjuvants (Quil A and pertussis toxin) to induce RR-EAE; sham-mice received adjuvants only. RR-EAE mice received subcutaneous ALA (3 or 10 mg kg(-1) day(-1)) or vehicle for 21 days (15-35 d.p.i.; [days postimmunization]); sham-mice received vehicle. Hindpaw hypersensitivity was assessed blinded using von Frey filaments. Following euthanasia (day 35 d.p.i.), lumbar spinal cords were removed for immunohistochemical and molecular biological assessments. Fully developed mechanical allodynia in the bilateral hindpaws of vehicle-treated RR-EAE mice was accompanied by marked CD3(+) T-cell infiltration, microglia activation, and increased brain-derived neurotrophic factor (BDNF)-tyrosine kinase B (TrkB) signaling in the dorsal horn of the lumbar spinal cord. Consequently, phospho-ERK, a marker of central sensitization in neuropathic pain, was upregulated in the spinal dorsal horn. Importantly, hindpaw hypersensitivity was completely attenuated in RR-EAE mice administered ALA at 10 mg kg(-1) day(-1) but not 3 mg kg(-1) day(-1). The antiallodynic effect of ALA (10 mg kg(-1) day(-1)) was associated with a marked reduction in the aforementioned spinal dorsal horn markers to match their respective levels in the vehicle-treated sham-mice. Our findings suggest that ALA at 10 mg kg(-1) day(-1) produced its antiallodynic effects in RR-EAE mice by reducing augmented CD3(+) T-cell infiltration and BDNF-TrkB-ERK signaling in the spinal dorsal horn.

Establishment and characterization of an optimized mouse model of multiple sclerosis-induced neuropathic pain using behavioral, pharmacologic, histologic and immunohistochemical methods.

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system (CNS) that causes debilitating central neuropathic pain in many patients. Although mouse models of experimental autoimmune encephalomyelitis (EAE) have provided insight on the pathobiology of MS-induced neuropathic pain, concurrent severe motor impairments confound quantitative assessment of pain behaviors over the disease course. To address this issue, we have established and characterized an optimized EAE-mouse model of MS-induced neuropathic pain. Briefly, C57BL/6 mice were immunized with MOG35-55 (200µg) and adjuvants comprising Quil A (45µg) and pertussis toxin (2×250ng). The traditionally used Freund's Complete Adjuvant (FCA) was replaced with Quil A, as FCA itself induces CNS neuroinflammation. Herein, EAE-mice exhibited a mild relapsing-remitting clinical disease course with temporal development of mechanical allodynia in the bilateral hindpaws. Mechanical allodynia was fully developed by 28-30days post-immunization (p.i.) and was maintained until study completion (52-60days p.i.), in the absence of confounding motor deficits. Single bolus doses of amitriptyline (1-7mg/kg), gabapentin (10-50mg/kg) and morphine (0.1-2mg/kg) evoked dose-dependent analgesia in the bilateral hindpaws of EAE-mice; the corresponding ED50s were 1.5, 20 and 1mg/kg respectively. At day 39 p.i. in EAE-mice exhibiting mechanical allodynia in the hindpaws, there was marked demyelination and gliosis in the brain and lumbar spinal cord, mirroring these pathobiologic hallmark features of MS in humans. Our optimized EAE-mouse model of MS-associated neuropathic pain will be invaluable for future investigation of the pathobiology of MS-induced neuropathic pain and for efficacy profiling of novel molecules as potential new analgesics for improved relief of this condition.