Allodynic Responses Research Articles

Allodynia Is Associated With Initial and Sustained Response to Acute Migraine Treatment: Results from the American Migraine Prevalence and Prevention Study.

In a population sample of persons with migraine treating with a single category of acute migraine medication, to identify rates and factors associated with acute treatment outcomes, including 2-hour pain freedom (2hPF), 24-hour pain response (24hPR), and 24-hour sustained pain response (24hSPR). Key predictors include acute treatment type (triptans and other medication categories), the influence of allodynia on response to medication, and the interaction between medication category and presence of allodynia in response to treatment among people with migraine. Cutaneous allodynia was previously associated with inadequate 2hPF, 24hPR, and 24hSPR (sustained response at 24 hours among those with adequate 2hPF) among people with migraine in the American Migraine Prevalence and Prevention (AMPP) Study. The AMPP Study obtained data from a representative US sample of persons with migraine by mailed questionnaire. The 2006 survey included 8233 people with migraine aged 18 or over who completed the Migraine Treatment Optimization Questionnaire (mTOQ). mTOQ was used to assess acute treatment outcomes including 2hPF, 24hPR, and 24hSPR. Eligible individuals used only a single category of acute prescription migraine treatments (n = 5236, 63.6%). This sample was stratified into 5 categories of type of acute prescription headache medication used (triptans, nonsteroidal anti-inflammatory drugs, barbiturate-combinations, opioids, and opioid combinations and ergot alkaloids). Separate binary logistic regression models evaluated: (1) triptans vs other medication types; (2) presence of allodynia vs no allodynia; and (3) the interaction of medication category with allodynia. Sociodemographic variables, health insurance status, over-the-counter and preventive medication use were included as covariates. Odds ratios (OR) and 95% confidence intervals (CI) were generated for each acute treatment outcome. Among eligible participants, the mean age was 46 years, and 82.5% were women. The triptan use group had better outcomes than other medication groups for 2hPF (OR range: 2.00-2.63, all significant except ergot alkaloids) and 24hPR (OR range: 2.10-6.22, all significant). No significant medication effects were found for the 24hSPR outcome. The presence of allodynia was associated with significantly worse outcomes for both 2hPF (OR range: 1.42-1.55, all significant) and 24hPR (OR range: 1.30-1.32, all significant, except for ergot alkaloids, P = .051). Allodynia effects were not significant for the 24hSPR. The interaction between medication and allodynia was also not significant (OR range for 2hPF: .68-2.02; OR range for 2hPR: .35-1.34; OR range for 24hSPR: 1.21-2.72) in any of the models, suggesting allodynia is an important predictor of treatment response regardless of the medication group prescribed. The use of triptan medication was associated with significantly better 2hPF (except vs ergot alkaloids) and significantly better 24hPR outcomes compared with other acute medication categories. The presence of allodynia significantly increased the likelihood of an inadequate treatment response for both of these outcomes. Triptan use was generally associated with the best outcomes. Because allodynia was associated with inadequate outcomes for all medication groups, we suggest that allodynia is an area of unmet treatment need.

Commensal bacterial modulation of the host immune response to ameliorate pain in a murine model of chronic prostatitis.

The human commensal microflora plays an essential role in modulating the immune response to control homeostasis. Staphylococcus epidermidis, a commensal bacterium most commonly associated with the skin exerts such effects locally, modulating local immune responses during inflammation and preventing superinfection by pathogens such as Staphylococcus aureus. Although the prostate is considered by many to be sterile, multiple investigations have shown that small numbers of gram-positive bacterial species such as S. epidermidis can be isolated from the expressed prostatic secretions of both healthy and diseased men. Chronic pelvic pain syndrome is a complex syndrome with symptoms including pain and lower urinary tract dysfunction. It has an unknown etiology and limited effective treatments but is associated with modulation of prostate immune responses. Chronic pelvic pain syndrome can be modeled using murine experimental prostatitis (EAP), where CD4+ve IL17A+ve T cells have been shown to play a critical role in disease orchestration and development of pelvic tactile allodynia. Here, we report that intraurethral instillation of a specific S. epidermidis strain (designated NPI [non-pain inducing]), isolated from the expressed prostatic secretion of a healthy human male, into EAP-treated mice reduced the pelvic tactile allodynia responses and increased CD4+ve IL17A+ve T-cell numbers associated with EAP. Furthermore, a cell wall constituent of NPI, lipoteichoic acid, specifically recapitulates these effects and mediates increased expression of CTLA4-like ligands PDL1 and PDL2 on prostatic CD11b+ve antigen-presenting cells. These results identify a new potential therapeutic role for commensal S. epidermidis NPI lipoteichoic acid in the treatment of prostatitis-associated pain.

Supradural inflammatory soup in awake and freely moving rats induces facial allodynia that is blocked by putative immune modulators

Facial allodynia is a migraine symptom that is generally considered to represent a pivotal point in migraine progression. Treatment before development of facial allodynia tends to be more successful than treatment afterwards. As such, understanding the underlying mechanisms of facial allodynia may lead to a better understanding of the mechanisms underlying migraine. Migraine facial allodynia is modeled by applying inflammatory soup (histamine, bradykinin, serotonin, prostaglandin E2) over the dura. Whether glial and/or immune activation contributes to such pain is unknown. Here we tested if trigeminal nucleus caudalis (Sp5C) glial and/or immune cells are activated following supradural inflammatory soup, and if putative glial/immune inhibitors suppress the consequent facial allodynia. Inflammatory soup was administered via bilateral indwelling supradural catheters in freely moving rats, inducing robust and reliable facial allodynia. Gene expression for microglial/macrophage activation markers, interleukin-1β, and tumor necrosis factor-α increased following inflammatory soup along with robust expression of facial allodynia. This provided the basis for pursuing studies of the behavioral effects of 3 diverse immunomodulatory drugs on facial allodynia. Pretreatment with either of two compounds broadly used as putative glial/immune inhibitors (minocycline, ibudilast) prevented the development of facial allodynia, as did treatment after supradural inflammatory soup but prior to the expression of facial allodynia. Lastly, the toll-like receptor 4 (TLR4) antagonist (+)-naltrexone likewise blocked development of facial allodynia after supradural inflammatory soup. Taken together, these exploratory data support that activated glia and/or immune cells may drive the development of facial allodynia in response to supradural inflammatory soup in unanesthetized male rats.

Effect of subacute agomelatine treatment on painful diabetic neuropathy: involvement of catecholaminergic mechanisms.

In this study, we investigated the effects of subacute agomelatine (40 and 80 mg/kg) administration on chronic hyperglycemia, metabolic parameters, and pain perception in streptozotocin-induced diabetic rats. Fasting blood glucose measurements and oral glucose tolerance tests were performed to evaluate the effect of agomelatine on glycemia, while metabolic parameters were monitored using metabolic cages. Potential effect of agomelatine on diabetes-induced mechanical and thermal allodynia was evaluated using dynamic plantar aesthesiometer and warm plate (38 °C) tests, respectively. Additionally, influence of agomelatine on hyperalgesia occurring in connection with diabetic neuropathy was examined using the Randall-Selitto (mechanical nociceptive stimulus), Hargreaves (thermal nociceptive stimulus), and cold plate (4 °C, thermal nociceptive stimulus) tests. Obtained data indicated that, in diabetic rats, agomelatine significantly improved hyperalgesia and allodynia responses, without no effect on hyperglycemia or the associated polydipsia, polyuria, and hyperphagia. Therapeutic potential of agomelatine on neuropathic pain was suppressed with α-methyl-para-tyrosine methyl ester (an inhibitor of catecholamine synthesis), phentolamine (a nonselective α-adrenoceptor antagonist), and propranolol (a nonselective β-adrenoceptor antagonist) administrations. However, p-chlorophenylalanine methyl ester (an inhibitor of serotonin synthesis) pretreatment could not be achieved to reverse these antihyperalgesic and antiallodynic effects. These results suggest that the curative effect of agomelatine on neuropathic pain is mediated through rising synaptic catecholamine levels as well as through interactions with both α- and β-adrenoceptors. To our knowledge, this is the first study to show findings that indicate catecholaminergic system mediated antihyperalgesic and antiallodynic effects of agomelatine.

Abstract PR149

Background & Objectives: Increased oxidative stress has been linked to anesthetics-induced nerve injury in a diabetic neuropathy (DN) rat model. The present study was aimed to investigate the effects of diphenyleneiodonium chloride (DPI), an NADPH oxidase (NOX) inhibitor on bupivacaine-induced sciatic nerve injury in DN rats. Materials & Methods: A rat DN model was established by high fat diet (HFD) feeding and streptozotocin (STZ) injection, and confirmed by blood glucose test, mechanical allodynia in response to von Frey (VF) filament stimulation, Paw withdrawal thermal latency (PWTL) test and nerve conduction velocity (NCV). Right sciatic nerve block was performed using 0.2 mL 0.5% bupivacaine. DPI (1mg/kg) was injected subcutaneously at 24 h and 30 min before nerve block. After 24 h of nerve block, nerve conduction function, sciatic nerve injury, levels of lipid peroxides and hydroperoxides, and expression of NOX2 and NOX4 was evaluated. Results: A rat model of DN was successfully established. Compared with the control group, the sensory and motor recovery time, and the value of VF and PWTL significantly raised, NCV of sciatic nerve significantly declined, and sciatic nerve injury was more severe in bupivacaine-treated DN group. DPI treatment significantly improved nerve function and injury. Compared with the bupivacaine-treated DN group, the levels of lipid peroxides and hydrperoxide, and the protein express of NOX2 and NOX4 significantly reduced in DPI group. Conclusion: Subcutaneous injection of DPI can effectively protect against the functional and neurohistological damage of sciatic nerves induced by bupivacaine in an HFD/STZ-induced DN model. Disclosure of Interest: None declared

Dural stimulation in rats causes brain-derived neurotrophic factor-dependent priming to subthreshold stimuli including a migraine trigger.

Migraine is one of the most common and most disabling disorders. Between attacks, migraine patients are otherwise normal but are sensitized to nonnoxious events known as triggers. The purpose of these studies was to investigate whether a headache-like event causes sensitization, or priming, to subsequent subthreshold events. Interleukin-6 (IL-6) was applied to the rat cranial dura mater which produced cutaneous facial and hind paw allodynia that lasted 24 hours. At 72 hours, IL-6-treated rats developed allodynia in response to dural stimulation with either a pH 6.8 or pH 7.0 solution and to a systemic nitric oxide (NO) donor, a well-known migraine trigger. Vehicle-treated rats did not respond to either pH stimulus or to the NO donor, demonstrating that IL-6 exposure primes rats to subthreshold stimuli. Inhibitors of brain-derived neurotrophic factor (BDNF) signaling given either systemically or intracisternally 24 hours after IL-6 eliminated responses to dural pH stimulation at 72 hours. Additionally, intracisternal administration of BDNF without previous dural stimulation produced allodynia and once resolved, animals were primed to dural pH 6.8/pH 7.0 and a systemic NO donor. Finally, hind paw IL-6 produced paw allodynia but not priming to paw injection of pH 7.0 at 72 hours demonstrating differences in priming depending on location. These data indicate that afferent input from the meninges produces BDNF-dependent priming of the dural nociceptive system. This primed state mimics the interictal period of migraine where attacks can be triggered by normally nonnoxious events and suggests that BDNF-dependent plasticity may contribute to migraine.

Diacylglycerol lipase β inhibition reverses nociceptive behaviour in mouse models of inflammatory and neuropathic pain.

Inhibition of diacylglycerol lipase (DGL)β prevents LPS-induced pro-inflammatory responses in mouse peritoneal macrophages. Thus, the present study tested whether DGLβ inhibition reverses allodynic responses of mice in the LPS model of inflammatory pain, as well as in neuropathic pain models. Initial experiments examined the cellular expression of DGLβ and inflammatory mediators within the LPS-injected paw pad. DAGL-β (-/-) mice or wild-type mice treated with the DGLβ inhibitor KT109 were assessed in the LPS model of inflammatory pain. Additional studies examined the locus of action for KT109-induced antinociception, its efficacy in chronic constrictive injury (CCI) of sciatic nerve and chemotherapy-induced neuropathic pain (CINP) models. Intraplantar LPS evoked mechanical allodynia that was associated with increased expression of DGLβ, which was co-localized with increased TNF-α and prostaglandins in paws. DAGL-β (-/-) mice or KT109-treated wild-type mice displayed reductions in LPS-induced allodynia. Repeated KT109 administration prevented the expression of LPS-induced allodynia, without evidence of tolerance. Intraplantar injection of KT109 into the LPS-treated paw, but not the contralateral paw, reversed the allodynic responses. However, i.c.v. or i.t. administration of KT109 did not alter LPS-induced allodynia. Finally, KT109 also reversed allodynia in the CCI and CINP models and lacked discernible side effects (e.g. gross motor deficits, anxiogenic behaviour or gastric ulcers). These findings suggest that local inhibition of DGLβ at the site of inflammation represents a novel avenue to treat pathological pain, with no apparent untoward side effects.

(357) Antinociceptive effects of a synthetic tetracycline compound on mechanical and cold allodynia

Synthetic tetracycline compounds have been developed and are able to reduce infection as well as inflammation. They are broad-spectrum antibiotics used against different bacterial infectious diseases. However, the effect on mechanical and cold pain sensitivity has not been investigated. The goal of the study is to evaluate the effect of synthetic tetracycline compounds with or without alcohol on mechanical and cold allodynia responses. Mechanical and cold responses will be used to evaluate pain threshold differences between male and female wild-type C57BL/6 mice. First, we have evaluated the effect of a synthetic tetracycline compound on mechanical and cold allodynia. Our data indicate that mechanical and cold allodynia remains unchanged after administration of a synthetic tetracycline compound meaning values are similar to baseline levels. However, synthetic tetracycline compound showed antinociceptive effects to mechanical and cold allodynia following the formalin test (60 minutes after injection of formalin). Moreover, mechanical and cold allodynia responses return to baseline levels 2 hours after the formalin test. Second, we have evaluated the effect of alcohol on mechanical and cold allodynia. Chronic alcohol lowers mechanical and cold allodynia thresholds differently in male and female mice. These results demonstrate potential antinociceptive properties of synthetic tetracycline compound in response to mechanical and cold allodynia. Further studies are needed to investigate the mechanism underlying this antinociceptive effect of synthetic tetracycline compounds and a possible gender specific difference. Antinociceptive properties of synthetic tetracycline compounds could be a great alternative avenue to alleviate pain in patients.

Antinociceptive effects of synthetic tetracycline compound and influence of Cx3cr1 in inflammatory pain

Tetracycline compounds are broad‐spectrum antibiotics used against different bacterial infectious diseases. Synthetic tetracycline compounds have been developed and are able to reduce infection as well as inflammation. However, the effect on alleviation of pain, and more specifically reduction of inflammatory pain, has not been investigated. The goal of the study is to evaluate the effect of synthetic tetracycline compounds using an inflammatory pain model and mechanical and cold allodynia responses. The formalin test (10 μl at 2.5 % intraplantar) was use to evaluate pain threshold differences between male wild‐type C57BL/6 mice and male GFP Cx3cr1 +/− mice. First, our preliminary data demonstrate that male GFP Cx3cr1 +/− mice show lower pain threshold in both (acute and inflammatory) phases of the formalin test. Second, we evaluated the effect of a synthetic tetracycline compound on inflammatory pain and on mechanical and cold allodynia. Our data indicate that mechanical and cold allodynia remains unchanged after administration of a synthetic tetracycline compound meaning values are similar to baseline levels. However, synthetic tetracycline compound lower pain threshold in both phases of the formalin test from 4 hours up to 20 hours after its administration and showed antinociceptive effects to mechanical and cold allodynia following the formalin test (60 minutes after injection of formalin). Moreover, mechanical and cold allodynia responses return to baseline levels 2 hours after the formalin test. These results demonstrate potential antinociceptive properties of synthetic tetracycline compound with long lasting effect up to 20 hours after its administration. Further studies are needed to investigate the mechanism underlying this antinociceptive effect of synthetic tetracycline compounds. We will also evaluate potential stronger antinociceptive effect of the synthetic tetracycline compound in Cx3cr1 +/− male mice and evaluate if there is any gender specific differences. Antinociceptive properties of synthetic tetracycline compound could be a great alternative avenue to relieve inflammatory pain and improve alleviation of pain in patients.Support or Funding InformationFunded by grant from NIAAA 021142 (SEB) and funded by Texas Tech University Health Sciences Center School of Medicine grant 121035 (JG).

IL-17 is not essential for inflammation and chronic pelvic pain development in an experimental model of chronic prostatitis/chronic pelvic pain syndrome.

Pain and inflammation in the absence of infection are hallmarks in chronic prostatitis and chronic pelvic pain syndrome (CP/CPPS) patients. The etiology of CP/CPPS is unclear, and autoimmunity has been proposed as a cause. Experimental autoimmune prostatitis (EAP) models have long been used for studying CP/CPPS. Herein, we studied prostate inflammation induction and chronic pelvic pain development in EAP using IL-12p40-KO, IL-4-KO, IL-17-KO, and wild-type (C57BL/6) mice. Prostate antigen (PAg) immunization in C57BL/6 mice induced specific Th1 and Th17 immune responses and severe prostate inflammation and cell infiltration, mainly composed of CD4 T cells and macrophages. Moreover, chronic pelvic pain was evidenced by increased allodynia responses. In immunized IL-17-KO mice, the presence of a prominent PAg-specific Th1 immune response caused similar prostate inflammation and chronic pelvic pain. Furthermore, markedly high PAg-specific Th1 immune responses, exacerbated prostate inflammation, and chronic pelvic pain were detected in immunized IL-4-KO mice. Conversely, immunized IL-12p40-KO mice developed PAg-specific Th2 immune responses, characterized by high IL-4 secretion and neither infiltration nor damage in the prostate. As observed in wild-type control animals, IL12p40-KO mice did not evidence tactile allodynia responses. Our results suggest that, as in patients, chronic pelvic pain is a consequence of prostate inflammation. After PAg immunization, a Th1-associated immune response develops and induces prostate inflammation and chronic pelvic pain. The absence of Th1 or Th2 cytokines, respectively, diminishes or enhances EAP susceptibility. In addition, IL-17 showed not to be essential for pathology induction and chronic pelvic pain development.

Abstract P1-15-07: The neuroprotective aminopropyl carbazole, P7C3-A20, prevents paclitaxel-induced pain

Abstract Paclitaxel (PTX), a microtubule-targeting anticancer agent, produces a debilitating peripheral neuropathy that is accompanied by neuropathic pain. Currently, there are only marginally effective therapeutic interventions available. Consequently, patients are forced to reduce or discontinue life-saving chemotherapy to cope with the pain. Recently, a newly identified agent, P7C3-A20, was found to be protective in several models of neurodegeneration, including Parkinson's disease and traumatic brain injury. Given that PTX triggers progressive degeneration of peripheral afferent neurons, this study was performed to evaluate the potential neuroprotective efficacy of P7C3-A20 in rodent models of PTX-induced peripheral neuropathy. P7C3-A20 (10 mg/kg) or vehicle (Cremophor EL/DMSO/5% Dextrose; 1:1:3) was administered intraperitoneally (i.p.) to Sprague-Dawley rats (250-300 g) everyday over a 28-day experimental paradigm. Following two days of treatment with P7C3-A20 or vehicle, rats also received 3 injections of PTX (11.7 mg/kg, i.p.) or vehicle (Cremophor EL/DMSO/5% Dextrose; i.p.) administered every other day. Treatment with P7C3-A20 did not alter body weights or leukocyte counts in control or PTX-treated rats. PTX treatment increased sensitivity to mechanical and cold stimulation (allodynia) of the hindpaw, evidence of peripheral neuropathy. Notably, P7C3-A20 treatment prevented the development of allodynia in response to PTX. Immunohistochemical analysis of paw biopsies indicated that P7C3-A20 prevented PTX-mediated degeneration of terminal nerve endings. Collectively, these data suggest that P7C3-A30 prevented the neurotoxic effects of PTX on peripheral sensory neurons. A xenograft tumor model of triple negative breast cancer was then used to determine whether P7C3-A20 diminished the antitumoral efficacy of PTX. MDA-MB-231 tumors were bilaterally implanted into flanks of female athymic nude mice and allowed to grow for 3 weeks prior to treatment. Using the same treatment protocol as the rats, tumor-bearing mice received daily treatment with P7C3-A20 (20 mg/kg, i.p.) or vehicle for 16 days. P7C3-A20 did not alter PTX-mediated inhibition of tumor growth. Furthermore, P7C3-A20 prevented PTX-induced mechanical allodynia in the mice. Taken together, this work indicates that P7C3-A20 prevents PTX-induced neuropathic damage without diminishing its antitumoral efficacy. P7C3-A20 may be an exciting new candidate to prevent peripheral neuropathy in patients undergoing cancer treatment with PTX. Citation Format: LoCoco PM, Risinger AL, Mooberry SL, Berg KA, Clarke WP. The neuroprotective aminopropyl carbazole, P7C3-A20, prevents paclitaxel-induced pain. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P1-15-07.

Uromastyx acanthinura as a natural treatment in a mouse model of type 2 diabetes

AimsOral testimonies from North Africa attribute anti-diabetic effects to medicinal preparations of the lizard Uromastyx acanthinura (UA). No scientific evidence of such effects is currently available. The acute effects of oral administration of UA to C57Bl/6J mice with diet-induced diabetes were tested and, if effectiveness was shown, the effect of subchronic UA administration was assessed in the same model. MethodsMice were fed a diet containing 60% fat for at least 12 weeks. To assess acute effects, different doses of UA or saline were orally administered with 2g of glucose/kg during an oral glucose tolerance test (OGTT) on different days in a randomised crossover design. The most effective dose was then fed together with the high-fat diet for 90 days and compared to high-fat diet alone in a parallel design. Body weight (BW), food consumption, welfare, and external appearance were assessed weekly. HbA1c, OGTT, and intraperitoneal insulin tolerance tests (IPITT) were performed at baseline and after treatment. Severity of neuropathy was evaluated by cold allodynia response in the acetone test. ResultsUA significantly decreased glucose levels as compared to saline 15min after administration. After 90 days of treatment, no differences were seen in OGTT or HbA1c between the groups, while IPITT showed higher glucose levels in UA-treated animals. Although weight increase was similar in both groups, weight tended to be higher in the treated group, which had a significantly higher daily food consumption. Cold allodynia response improved in frequency and intensity in the UA group. ConclusionsOrally administered UA acutely decreased blood glucose in diabetic mice. Paradoxically, long-term administration of UA increased food consumption, weight, and insulin resistance. Improved nociceptive response suggested an effect on pain and/or neuropathy. Although additional studies are needed to elucidate the properties and potential applications of UA, our results highlight the value of ethnomedical approaches to African traditional medicine as starting point to evaluate new bioactive components.

Prokineticin 2 facilitates mechanical allodynia induced by α,β-methylene ATP in rats

Prokineticin 2 (PK2), a new chemokine, causes mechanical hypersensitivity in the rat hind paw, but little is known about the molecular mechanism. Here, we have found that ionotropic P2X receptor is essential to mechanical allodynia induced by PK2. First, intraplantar injection of high dose (3 or 10pmol) of PK2 significantly increased paw withdrawal response frequency (%) to innocuous mechanical stimuli (mechanical allodynia). And the mechanical allodynia induced by PK2 was prevented by co-administration of TNP–ATP, a selective P2X receptor antagonist. Second, although low dose (0.3 or 1pmol) of PK2 itself did not produce an allodynic response, it significantly facilitated the mechanical allodynia evoked by intraplantar injection of α,β-methylene ATP (α,β-meATP). Third, PK2 concentration-dependently potentiated α,β-meATP-activated currents in rat dorsal root ganglion (DRG) neurons. Finally, PK2 receptors and intracellular signal transduction were involved in PK2 potentiation of α,β-meATP-induced mechanical allodynia and α,β-meATP-activated currents, since the potentiation were blocked by PK2 receptor antagonist PKRA and selective PKC inhibitor GF 109203X. These results suggested that PK2 facilitated mechanical allodynia induced by α,β-meATP through a mechanism involved in sensitization of cutaneous P2X receptors expressed by nociceptive nerve endings.

Treatment for neuropathic pain and chronic inflammation using LASER in animal models.

The ST36 (Zusanli) acupuncture point is used to treat inflammatory processes, pain and gastrointestinal disturbs. For this reason, the aim of the present study was to evaluate the antinociceptive effect of Low-level Laser Treatment (LLLT) on ST36 acupoint using models of chronic nociception and inflammation. Male Swiss mice were treated with LLLT on ST36 30 minutes before the mechanical allodynia (von Frey) performed on the partial sciatic nerve ligation (PSNL) method and Complete Freund's Adjuvant (CFA). The results demonstrated that application of LLLT on ST36 inhibited the mechanical allodynia response induced by PSNL and CFA, with total reversion at 30 minutes after application. Long-term treatment of animals with LLLT on the same acupoint, once a day, also reduced the PNSL and CFA-induced mechanical allodynia response during 8 days of treatment. As conclusion, the results demonstrated that photonic stimulus on ST36 with LLLT produces antinociceptive effect in chronic models of nociception and inflammation. These findings suggest that LLLT may constitute an important therapeutic alternative to control chronic pain.

Analysis of the anti-inflammatory and chemopreventive potential and description of the antimutagenic mode of action of the Annona crassiflora methanolic extract

Context: Annona crassiflora Mart. (Annonaceae) is a medicinal plant that is widely used in folk medicine, which leads to its investigation as a potential source of new pharmacological principles.Objective: This study describes the anti-inflammatory, antiallodynic, and antimutagenic/chemopreventive activities of the leaves A. crassiflora methanolic extract. Its antimutagenic mode of action was analyzed in a plant or animal experimental model.Materials and methods: Total flavonoids were quantified by spectrophotometry at 415 nm and its composition was analyzed by 1H NMR spectra. Animals received orally, 30, 100, and 300 mg/kg of extract in both tests, carrageenan-induced paw edema and myeloperoxidase activity. Animals were treated with 100 and 300 mg/kg, in all the analyzed tests, pleural cell migration and protein exudation, carrageenan-induced cell migration into the pouch, induction of joint inflammation and carrageenan-induced allodynia response in the mouse paw. To evaluate the antimutagenic/chemopreventive activity through the Allium cepa test, we used 5, 10, and 15 mg/L of extract, and for the micronucleus test in the peripheral blood, we used the dose of 15 mg/kg.Results: The fractionation of the ethyl acetate (EA) fraction, resulting from the partition of the methanol extract of the A. crassiflora, afforded through chromatographic methods resulted in the isolation of kaempferol 3-O-β-glucoside and kaempferol 3-O-β-diglucoside. Oral treatment with 100 and 300 mg/kg of extract significantly inhibited the carrageenan-induced edema formation, with inhibitions of 53 ± 7% and 47 ± 10%; in MPO activity, the observed inhibitions were 60 ± 7% for 100 mg/kg treatment and 63 ± 7% for 300 mg/kg. The ACME reduced significantly the total leukocytes (an inhibition of 78 ± 9% with 100 mg/kg and 90 ± 7% with 300 mg/kg) and protein levels (approximately 100% inhibition with both doses) in the pleurisy model. In carrageenan-induced leukocyte migration into the pouch, the extract inhibited leukocyte migration only when administered 300 mg/kg per dose (the reduction was 43 ± 5%). Pretreatment with extract failed to reduce the zymosan-induced edema formation and did not inhibit the carrageenan-induced mechanical allodynia. Damage reduction in Allium cepa tested with different concentrations (5, 10, and 15 mg/L) was 66.17, 75.75, and 69.19% for the pre-treatment; 72.72, 33.33, and 22.22% for the simple simultaneous treatment; 100.50, 93.93, and 102.52% for the simultaneous treatment with pre-incubation; 89.39, 79.79, and 84.34%; for the post-treatment, and 86.36, 81.31, and 93.43% for the continuous treatment. The antimutagenic evaluation in the micronucleous test showed a damage reduction of 75.00 and 64.58% for the pre-treatment and simultaneous protocols, respectively. The post-treatment protocol increased the cyclophosphamide effects in 45.83%.Conclusion: These results suggest that this medicinal plant has chemopreventive and anti-inflammatory therapeutic potential.

Tactile allodynia in patients with lumbar radicular pain (sciatica)

We report a novel symptom in many patients with low back pain (LBP) that sheds new light on the underlying pain mechanism. By means of quantitative sensory testing, we compared patients with radicular LBP (sciatica), axial LBP (LBP without radiation into the leg), and healthy controls, searching for cutaneous allodynia in response to weak tactile and cooling stimuli on the leg and low back. Most patients with radicular pain (~60%) reported static and dynamic tactile allodynia, as well as cooling allodynia, on the leg, often extending into the foot. Some also reported allodynia on the low back. In axial LBP, allodynia was almost exclusively on the back. The degree of dynamic tactile allodynia correlated with the degree of background pain. The presence of allodynia suggests that the peripheral nerve generators of background leg and back pain have also induced central sensitization. The distal (foot) location of the allodynia in patients who have it indicates that the nociceptive drive that maintains the central sensitization arises paraspinally (ectopically) in injured ventral ramus afferents; this is not an instance of somatic referred pain. The presence of central sensitization also provides the first cogent account of shooting pain in sciatica as a wave of activity sweeping vectorially across the width of the sensitized dorsal horn. Finally, the results endorse leg allodynia as a pain biomarker in animal research on LBP, which is commonly used but has not been previously validated. In addition to informing the underlying mechanism of LBP, bedside mapping of allodynia might have practical implications for prognosis and treatment. Social media questionHow can you tell whether pain radiating into the leg in a patient with sciatica is neuropathic, ie, due to nerve injury?

Chronic pelvic allodynia is mediated by CCL2 through mast cells in an experimental autoimmune cystitis model.

The cause of chronic pelvic pain in interstitial cystitis/painful bladder syndrome (IC/PBS) remains unclear; autoimmunity is a possible etiology. We have recently shown that injection of a single immunogenic peptide of uroplakin 3A (UPK3A 65-84) induces experimental autoimmune cystitis (EAC) in female BALB/cJ mice that is unique among experimental models in accurately reflecting both the urinary symptoms and pelvic pain of IC/PBS. The aim of this project was to identify the roles of mast cells and mast cell chemoattractant/activator monocyte chemoattractant protein-1 [chemokine (C-C motif) ligand 2 (CCL2)] in the allodynia in this model. We immunized 6- to 8-wk-old female BALB/cJ mice with UPK3A 65-84 peptide and, 5-40 days later, observed increased responses to stimulation of the suprapubic abdominal and hindpaw surfaces with von Frey monofilaments compared with mice injected with adjuvant alone. Suprapubic and hindpaw tactile allodynia responses by EAC mice were blocked by instillation of lidocaine into the bladder but not by lidocaine in the uterus, confirming the bladder as the source of the hypersensitivity. Markedly increased numbers of activated mast cells and expression of CCL2 were found in the bladder after immunization with UPK3A 65-84. Hypersensitive responses were inhibited by mast cell stabilizer cromolyn sodium and antagonists of histamine receptors 1 and 2. Furthermore, BALB/cJ mice with deletion of the Ccl2 or chemokine (C-C motif) receptor 2 gene exhibited markedly reduced allodynia and accumulation of mast cells after UPK3A 65-84 immunization. These results show that UPK3A 65-84 immunization causes chronic visceral allodynia and suggest that it is mediated by CCL2-driven mast cell accumulation in the bladder.

Therapeutic efficacy of dezocine for the treatment of the co-morbidity of neuropathic pain and itching in mice

Objective To observe the therapeutic efficacy of dezocine on the treatment for the co-morbidity of pain-itch (CPI) which were induced by spared nerve injuries (SNI) and evoked by chloroquine intradermal injections.Methods Adult male Kun-Ming mice (SPF grade,22 g-26 g) were assigned randomly into six groups (n=8):group A (Sham+NS+NS),group B (SNI+ NS+NS),group C (SNI+Itch+NS),group D (Sham+Itch+NS),group E (SNI+Itch+Dezocine),and group F (Sham+Itch+Dezocine).Mechanical allodynia was assessed using electron-Von Frey.To test pain threshold,Paw withdrawal threshold (PWT,to assess mechanical allodynia) was measured by electro von Frey on-1 d (baseline),1,3 d,and 5 d (before and after dezocine and chloroquine intradermal injection).Scratching behaviors of animals were video-recorded to analysis chloroquine-evoked itching in each group.Results Compared with the area under curve (AUC) of PWT for mechanical allodynia or analgesic responses,group A-AUC＜group B-AUC (P＜0.05).Scratching latency (SL):group A (49± 11) s,group B (51 ± 10) s,group C (322± 127) s,group D (333±94) s,group E(571±67) s,group F(524±77) s,SL in group E or F of dezocine therapy were prolonged significantly compared to group C and D(P＜0.05).The number of scratching:group C(13.7±3.4),group D(25.8±5.2),group E(5.8±2.0),group F(6.3± 1.8),The number of scratching in group C (13.7±3.4) was significantly reduced compared to group D(13.7±3.4) vs (25.8±5.2)(P＜ 0.05).And the number of scratching in group E(5.8±2.0) or group F(13.7±3.4) was both reduced significantly compared to group C and D (P＜0.05).Conclusions These data suggest that dezocine is a highly efficacious analgesic and antipruritic treatment for the CPI in mice. Key words: Neuropathic pain; Itch; Co-morbidity; Dezocine

Dopaminergic modulation of neuropathic pain: analgesia in rats by a D2-type receptor agonist.

Experimental studies have shown that dopaminergic mechanisms can modulate both nociception and chronic pain perception, but such property is not exploited pharmacologically at the clinical level. We have previously shown that levodopa produces D2-receptor-mediated antiallodynic effects in rats with peripheral mononeuropathy. Here, we test the effects of a D2-type receptor (D2R) agonist, quinpirole, on neuropathic pain in rats. Allodynic responses to cooling and light touch were measured in the hind limbs of rats with chronic constriction injury of one sciatic nerve. Single intraperitoneal injection of quinpirole (1 mg/kg) totally inhibited cold and tactile allodynic responses for over 3 and 48 h, respectively. At that dose, quinpirole had no effect on nocifensive responses to heat. Lumbar intrathecal injection of quinpirole produced short-term inhibition of the responses to cold and tactile stimuli, suggesting that spinal mechanisms may contribute to the antiallodynic activity of quinpirole. Chronic subcutaneous infusion of quinpirole by implanted Alzet pumps (0.025 mg/kg·day) provided a slowly progressing inhibition of cold and tactile allodynic responses, which re-emerged after the pumps were removed. These experiments show the involvement of dopaminergic systems in the modulation of chronic allodynias and provide experimental support for proposing the use of D2R agonists for neuropathic pain relief.

μ-Opioid activation in the midbrain during migraine allodynia - brief report II.

We investigated in vivo the allodynic response of the central μ-opioid system during spontaneous migraine headaches, following a sustained pain threshold challenge on the trigeminal ophthalmic region. Six migraineurs were scanned during the ictal and interictal phases using positron emission tomography (PET) with the selective μ-opioid receptor (μOR) radiotracer [11C]carfentanil. Females were scanned during the mid-late follicular phase of two separate cycles. Patients showed ictal trigeminal allodynia during the thermal challenge that was concurrent and positively correlated with μOR activation in the midbrain, extending from red nucleus to ventrolateral periaqueductal gray matter. These findings demonstrate for the first time in vivo the high μOR activation in the migraineurs' brains in response to their allodynic experience.