The antinociceptive effects of gabapentin and nitric oxide on neuropathic pain model formed in rats

Çalışmamızda ratlarda oluşturulan nöropatik ağrı modelinde gabapentin ve nitrik oksitin etkilerini araştırmayı amaçladık. Yöntem ve Gereç: Çalışma, Adnan Menderes Üniversitesi Tıp Fakültesi Deney Hayvanları Etik Kurulu onayı alındıktan sonra, Tıp Fakültesi Fizyoloji Deneysel Araştırma laboratuarında gerçekleştirildi. Ağırlıkları 250-350 gr arasında değişen Wistar cinsi 63 erkek rat randomize olarak dokuz eşit gruba (n=7) ayrıldı. Tüm gruplardaki ratların başlangıçta ve deneyin sonunda kiloları ölçüldü. Kontrol grubu dışında tüm gruplardaki ratlarda Bennett ve Xie tarafından tarif edilen siyatik sinir ligasyonu ile CCI (Kronik Sıkıştırma Hasarı) modelinin modifiye şekli uygulanarak nöropatik ağrı oluşturuldu. Grup 0 kontrol grubu olarak alındı. Grup SF'e serum fizyolojik, Grup G30'a gabapentin 30 mg/kg, Grup G30+NO'ya gabapentin 30mg/kg +nitrogliserin 1mg/kg, Grup G100'e gabapentin 100 mg/kg, Grup G100+NO'ya gabapentin 100 mg/kg +nitrogliserin 1mg/kg, Grup G300'e gabapentin 300mg/kg, Grup G300+NO'ya gabapentin 300mg/kg +nitrogliserin1mg/kg, Grup NO'ya ise nitrogliserin 1 mg/kg periton içine 21 gün süreyle verildi. Ratların her 10 gramı için 0.07 mL ilaç uygulandı. Deney süresince ratların hareketleri izlendi. Beşinci, onuncu, onbeşinci ve yirmibirinci günlerde von Frey testi yapıldı. Yirmibirinci günde hot-plate testi yapıldı. Bulgular: Beşinci ve onuncu günlerdeki Von Frey ölçümlerinde en yüksek değerlere G30+NO grubunda çıkıldığı gözlendi. Gabapentinin daha yüksek dozlarda verildiği gruplarda von Frey ölçümlerinde elde edilen değerler düşüktü. Hot-plate testinde ise en uzun süre G30 grubunda elde edildi. Sonuç: Ratlarda oluşturduğumuz deneysel nöropatik ağrı modelinde gabapentin intraperitoneal 30 mg/kg+NO 1mg/kg dozunun nöropatik ağrıda mekanik hiperaljezi tedavisinde en etkili olduğu saptandı. Ayrıca gabapentinin 30 mg/kg dozunun termal hiperaljezide en etkili olduğu tespit edildi.To search the effects of gabapentin and nitric oxide on the neuropathic pain model which is made in rats. Material and method: The ethical committe permisssion was obtained from The Genuine Animals Ethic Committee. Wistar type 63 male rats, each of which weighed between 250-350 gr. are divided in to nine equal groups (n=7). Neuropathic pain was constituted at the rats except the control group, by syatic nerve ligation as modified form of CCI (Chronic Constriction Injury) model. Group 0 was the control group. Physiological serum was administered to Group SF. Gabapentin was administered; 30 mg/kg, 100 mg/k, 300 mg/kg to groups G30, G100, G300 respectively. Nitroglycerine was added 1 mg/kg to groups G30+NO, G100+NO, G300+NO respectively. One mg/kg nitroglycerine was administered to Group NO. Drugs were administered intraperitoneally for 21 days. At the fifth, tenth, fifteenth and twentyfirst days; the von Frey test was done. At the twentyfirst day of the study the hot-plate test was done. Findings: The highest values were obtained at the G30+NO group after the von Frey test at the fifth and tenth days. At the groups in which the gabapentin was administered at higher doses the values of the von Frey test were lower. The longest time was obtained at G30 at hot-plate test. Result: At the experimental neuropathic pain model; we found that, administration of 30 mg/kg gabapentin+1 mg/kg nitroglycerin intraperitonealy is the most effective at the treatment of mechanical hiperalgesia. Also it was found that 30 mg/kg gabapentin is the most effective at thermal hiperalgesia

Effects of vortioxetine in animal model of migraine

Увод: Мигрена је препозната као један од водећих здравствених проблема на глобалном нивоу, јер је праћена онеспособљеношћу и нарушеним квалитетом живота оболелих. Преко 50% пацијената са мигреном није задовољно својим лечењем. Постоје докази о ефикасности антидепресива, посебно оних са мултимодалним дејством (амитриптилин), и препоруке за њихову примену у профилакси мигренозне главобоље. Вортиоксетин је нови мултимодални антидепресив са недавно постулираним аналгетским својствима. Циљ рада: 1) Испитати аналгетску ефикасност вортиоксетина у поређењу са суматриптаном након пероралне акутне примене у моделу акутне мигренозне главобоље; 2) Испитати аналгетску ефикасност вортиоксетина у поређењу са пропранололом након поновљене профилактичке пероралне примене у моделу хроничне мигрене. Материјал и методе: Модел акутне мигренозне главобоље постављен је акутном применом нитроглицерина (10 mg/kg, интраперитонеално), док је модел хроничне мигрене постављен поновљеном, интермитентном применом нитроглицерина, сваког другог дана у деветодневним циклусима код мужјака мишева C57BL/6 соја. Поновљена примена нитроглицерина доводи до развоја хроничне базалне и акутне болне преосетљивости. За процену развоја болне преосетљивости, као и антиноцицептивног дејства испитиваних третмана, коришћени су тестови провоцираног болног понашања (von Frey тест – механички стимулус и орофацијални глутаматни тест – хемијски стимулус), као и тест непровоцираног болног понашања (тест копања), који је уједно одраз опште добробити животиња. Добијени резултати анализирани су применом једнофакторске/двофакторске ANOVA-е (уз Tukey post hoc анализу). Резултати: У моделу акутне мигренозне главобоље забележен је статистички значајан, упоредив (von Frey тест) или већи (орофацијални глутаматни тест) антиноцицептивни ефекат вортиоксетина у односу на суматриптан. У моделу хроничне мигрене показан је статистички значајан, упоредив (von Frey тест – базална преосетљивост, орофацијални глутаматни тест и тест копања) или већи (von Frey тест – акутна преосетљивост) антиноцицептивни ефекат вортиоксетина у односу на пропранолол. Закључак: Приказани резултати указују да је вортиоксетин је барем поредбено ефикасан као и референтни лекови за контролу мигренозних атака/профилаксу мигрене, што је налаз од могућег клиничког значаја.Introduction: Мigraine is recognized as a global health issue, responsible for high population levels of disability and impaired well-being. Above 50% of migraine sufferers are not satisfied with their pain relief strategies. There is evidence of antidepressants’ efficacy, especially those with multimodal action (amitriptyline), and recommendations for their use in migraine prophylaxis. Vortioxetine is a novel multimodal antidepressant with recently postulated analgesic properties. The Aim: 1) To examine the efficacy of vortioxetine compared to sumatriptan after acute oral administration in a migraine attack model; and 2) to examine the efficacy of vortioxetine compared to propranolol after repeated prophylactic oral administration in a chronic migraine model. Material and Methods: The model of a migraine attack was established by acute nitroglycerin injection (10 mg/kg, intraperitoneally), whereas the model of chronic migraine was developed by repeated, intermittent administration of nitroglycerin, every other day, over 9 days in male mice, C57BL/6 strain. Repeated nitroglycerin administration causes chronic basal and acute hypersensitivity. To assess the development of painful hypersensitivity, and the antinociceptive effects of corresponding treatments, stimulus-evoked tests (von Frey test – mechanical stimulus; orofacial glutamate test – chemical stimulus), and non-evoked nociceptive test (burrowing test; also reflecting general animal welfare) were used. The results were analyzed by one-way/two-way ANOVA (Tukey post hoc analysis). Results: In the migraine attack model, statistically significant, comparable (von Frey test) or higher (orofacial glutamate test) antinociceptive effects of vortioxetine compared to sumatriptan was observed. In the chronic migraine model, vortioxetine showed statistically significant, comparable (von Frey test – basal hypersensitivity, orofacial glutamate and burrowing tests) or higher (von Frey test – acute hypersensitivity) antinociceptive effects compared to propranolol. Conclusion: The presented results imply that vortioxetine is at least comparably effective as selected referent drugs for migraine attack/migraine prophylaxis treatment, giving clinical importance to our findings

An interleukin-33/ST2 signaling deficiency reduces overt pain-like behaviors in mice

Interleukin (IL)-33, the most recent member of the IL family of cytokines, signals through the ST2 receptor. IL-33/ST2 signaling mediates antigen challenge-induced mechanical hyperalgesia in the joints and cutaneous tissues of immunized mice. The present study asked whether IL-33/ST2 signaling is relevant to overt pain-like behaviors in mice. Acetic acid and phenyl-p-benzoquinone induced significant writhing responses in wild-type (WT) mice; this overt nociceptive behavior was reduced in ST2-deficient mice. In an antigen-challenge model, ST2-deficient immunized mice had reduced induced flinch and licking overt pain-like behaviors. In the formalin test, ST2-deficient mice also presented reduced flinch and licking responses, compared with WT mice. Naive WT and ST2-deficient mice presented similar responses in the rota-rod, hot plate, and electronic von Frey tests, indicating no impairment of motor function or alteration in basal nociceptive responses. The results demonstrate that IL-33/ST2 signaling is important in the development of overt pain-like behaviors

Sex differences in mechanical allodynia: how can it be preclinically quantified and analyzed?

Extent: 16 p.Translating promising preclinical drug discoveries to successful clinical trials remains a significant hurdle in pain research. Although animal models have significantly contributed to understanding chronic pain pathophysiology, the majority of research has focused on male rodents using testing procedures that produce sex difference data that do not align well with comparable clinical experiences. Additionally, the use of animal pain models presents ongoing ethical challenges demanding continuing refinement of preclinical methods. To this end, this study sought to test a quantitative allodynia assessment technique and associated statistical analysis in a modified graded nerve injury pain model with the aim to further examine sex differences in allodynia. Graded allodynia was established in male and female Sprague Dawley rats by altering the number of sutures placed around the sciatic nerve and quantified by the von Frey test. Linear mixed effects modeling regressed response on each fixed effect (sex, oestrus cycle, pain treatment). On comparison with other common von Frey assessment techniques, utilizing lower threshold filaments than those ordinarily tested, at 1 s intervals, appropriately and successfully investigated female mechanical allodynia, revealing significant sex and oestrus cycle difference across the graded allodynia that other common behavioral methods were unable to detect. Utilizing this different von Frey approach and graded allodynia model, a single suture inflicting less allodynia was sufficient to demonstrate exaggerated female mechanical allodynia throughout the phases of dioestrus and pro-oestrus. Refining the von Frey testing method, statistical analysis technique and the use of a graded model of chronic pain, allowed for examination of the influences on female mechanical nociception that other von Frey methods cannot provide.Lauren Nicotra, Jonathan Tuke, Peter M. Grace, Paul E. Rolan and Mark R. Hutchinso

Facial grimace testing as an assay of neuropathic pain-related behavior in a mouse model of cervical spinal cord injury.

A major portion of individuals affected by traumatic spinal cord injury (SCI) experience one or more types of chronic neuropathic pain (NP), which is often intractable to currently available treatments. The availability of reliable behavioral assays in pre-clinical models of SCI-induced NP is therefore critical to assess the efficacy of new potential therapies. Commonly used assays to evaluate NP-related behavior in rodents, such as Hargreaves thermal and von Frey mechanical testing, rely on the withdrawal response to an evoked stimulus. However, other assays that test spontaneous/non-evoked NP-related behavior or supraspinal aspects of NP would be highly useful for a more comprehensive assessment of NP following SCI. The Mouse Grimace Scale (MGS) is a tool to assess spontaneous, supraspinal pain-like behaviors in mice; however, the assay has not been characterized in a mouse model of SCI-induced chronic NP, despite the critical importance of mouse genetics as an experimental tool. We found that beginning 2 weeks after cervical contusion, SCI mice exhibited increased facial grimace features compared to laminectomy-only control mice, and this grimace phenotype persisted to the chronic time point of 5 weeks post-injury. We also found a significant relationship between facial grimace score and the evoked forepaw withdrawal response in both the Hargreaves and von Frey tests at 5 weeks post-injury when both laminectomy-only and SCI mice were included in the analysis. However, within only the SCI group, there was no correlation between grimace score and Hargreaves or von Frey responses. These results indicate both that facial grimace analysis can be used as an assay of spontaneous NP-related behavior in the mouse model of SCI and that the information provided by the MGS may be different than that provided by evoked tests of sensory function

Isoflurane and the analgesic effect of acupuncture and electroacupuncture in an animal model of neuropathic pain

The present study aimed to determine whether isoflurane interferes with the analgesic effects of acupuncture (Ac) and electroacupuncture (EA), using a neuropathic pain (NP) rat model. In total, 140 male Wistar rats were used; isoflurane-induced nociceptive response was evaluated using the von Frey test, serum calcium-binding protein b (S100b) levels and nerve growth factor (NGF) levels in the left sciatic nerve. The NP model was induced by chronic constriction injury of the sciatic nerve at 14 days after surgery. Treatment was initiated after NP induction with or without isoflurane anesthesia (20 min/ day/8 days). The von Frey test was performed at baseline, 14 days postoperatively, and immediately, 24 h, and 48 h after the last treatment. Results of the nociceptive test and three-way analysis of variance were analyzed by generalized estimating equations, the Bonferroni test, followed by StudenteNewmaneKeuls or Fisher’s least significant difference tests for comparing biochemical parameters (significance defined as p 0.05). At baseline, no difference was noted in the nociceptive response threshold among all groups. Fourteen days after surgery, compared with other groups, NP groups showed a decreased pain threshold, confirming establishment of NP. Ac and EA enhanced the mechanical pain threshold immediately after the last session in the NP groups, without anesthesia. Isoflurane administration caused increased nociceptive threshold in all groups, and this effect persisted for 48 h after the last treatment. There was an interaction between the independent variables: pain, treatments, and anesthesia in serum S100b levels and NGF levels in the left sciatic nerve. Isoflurane enhanced the analgesic effects of Ac and EA and altered serum S100b and left sciatic nerve NGF levels in rats with NP

Correlation between neurotrophic activity and sensitivity to mechanical stimuli in immobilization stress model treated with transcranial direct current stimulation

Stress causes biochemical and behavioral changes that can contribute to the genesis of diseases. Transcranial direct current stimulation modulates neuronal excitability. In the present study, the hypothesis that there is a correlation between the effects of tDCS on neurotrophic activity and the ability to increase the threshold for mechanical sensitivity was tested. Male Wistar rats were divided into ten groups: 1) Behavioral control (BeC); 2) Biochemical control (BiC); 3) Immobilization 30 (IMO30); 4) Immobilization 60 (IMO60); 5) Immobilization 120 (IMO120); 6) Immobilization 24h (IMO24h); 7) Immobilization + tDCS 30 (IMO+tDCS30); 8) Immobilization + tDCS 60 (IMO+tDCS60); 9) Immobilization + tDCS 120 (IMO+tDCS120); 10) Immobilization + tDCS 24h (IMO+tDCS24). Afterwards, they were submitted to the von Frey baseline behavioral test. In the following six days, they were submitted to the stress model by immobilization. On the seventh day, they received the last immobilization with the application of 20 minutes of tDCS or false stimulation with disconnected electrodes. Immediately after, they were subjected to the von Frey test 30, 60, 120 minutes and 24 hours after the session, then killed by decapitation with spinal cord collection for biochemical analysis. BDNF levels cord were assessed by Enzyme Linked Immunosorbent Assay (ELISA). There was a negative correlation between BDNF levels and mechanical sensitivity. The result show that tDCS can be an option to prevent effects of stress, however, studies still need to define adequate doses that the increase in BDNF is not exacerbated to the point of reducing the nociceptive threshold

Akut ve nöropatik ağrıda morfine bağlı antinosisepsiyonda Kv7 potasyum kanallarının rolü

Objective: We aimed to investigate the role of K(v)7 potassium channels in the morphine-induced antinociception in both acute and neuropathic pain models. Methods: Neuropathic pain was induced by partial ligation of the right sciatic nerve. For intracerebroventricular (i.c.v.) injections, each rat was equipped with a permanent cannula. The response to painful thermal stimuli was assessed by the tail-flick test. In sciatic nerve-ligated rats, thermal hyperalgesia was assessed by paw withdrawal latencies in the plantar test and the mechanical hyperalgesia was determined by rigid von Frey filaments. Results: Rats received morphine (2, 5, 20 mu g/10 mu l; i.c.v.) or saline (10 mu l; i.c.v.) 15 min before the tests. In all tests, morphine produced significant antinociceptive effect. When a K(v)7 potassium channel blocker, linopirdine (0.1, 1, 10 mu g/10 mu l; i.c.v.) was administered 15 min before morphine, the effect of i.c.v. morphine in the tail-flick test and plantar test but not in the test with von Frey filaments were prevented. Conclusions: K(v)7 potassium channels contribute to the effect of i.c.v. morphine on acute pain induced by thermal stimulation. In the sciatic nerve-ligated rats, these channels play role in the effect of morphine on thermal hyperalgesia, but not on mechanical hyperalgesia.Akut ve nöropatik ağrı modellerinde morfine bağlı antinosisepsiyonda Kv7 potasyum kanallarının rolünü araştırmayı amaçladık. Materyal ve Metod: Nöropatik ağrı oluşturmak için sağ siyatik sinire parsiyel ligasyon uygulandı. Intraserebroventriküler (i.c.v.) enjeksiyonlar için, her sıçana kalıcı kanül takıldı. Ağrılı termal uyarana yanıt tail-flick testi ile değerlendirildi. Siyatik sinir ligasyonu yapılan sıçanlarda, termal hiperaljezi plantar testte pençe çekme latansı ile, mekanik hiperaljezi ise rijid von Frey filamanları ile değerlendirildi. Bulgular: Sıçanlara testlerden 15 dakika önce morfin (2, 5, 20 µg/10 µl; i.c.v.) veya salin (10 µl; i.c.v.) uygulandı.Tüm testlerde morfin anlamlı antinosiseptif etki gösterdi. Bir Kv7 potasyum kanal blokeri olan linopirdin (0.1, 1, 10 µg/10 µl; i.c.v.) morfinden 15 dakika önce uygulandığında, i.c.v. morfinin tail-flick ve plantar testte görülen etkilerini önlerken, von Frey filamanları ile yapılan test üzerine etkilerini değiştirmedi. Sonuç: Kv7 potasyum kanalları termal stimülasyona bağlı akut ağrıda i.c.v. morfinin etkisine katılmaktadırlar. Siyatik sinir ligasyonlu sıçanlarda, bu kanallar, morfinin termal hiperaljeziye etkisinde rol oynarken, mekanik hiperaljezi üzerine etkisinde rolü yoktur

Quick discrimination of A delta and C fiber mediated pain based on three verbal descriptors

Background: A delta and C fibers are the major pain-conducting nerve fibers, activate only partly the same brain areas, and are differently involved in pain syndromes. Whether a stimulus excites predominantly A delta or C fibers is a commonly asked question in basic pain research but a quick test was lacking so far. Methodology/Principal Findings: Of 77 verbal descriptors of pain sensations, "pricking", "dull" and "pressing" distinguished best (95% cases correctly) between A delta fiber mediated (punctate pressure produced by means of von Frey hairs) and C fiber mediated (blunt pressure) pain, applied to healthy volunteers in experiment 1. The sensation was assigned to A delta fibers when "pricking" but neither "dull" nor "pressing" were chosen, and to C fibers when the sum of the selections of "dull" or "pressing" was greater than that of the selection of "pricking". In experiment 2, with an independent cohort, the three-descriptor questionnaire achieved sensitivity and specificity above 0.95 for distinguishing fiber preferential non-mechanical induced pain (laser heat, exciting A delta fibers, and 5-Hz electric stimulation, exciting C fibers). Conclusion: A three-item verbal rating test using the words "pricking", "dull", and "pressing" may provide sufficient information to characterize a pain sensation evoked by a physical stimulus as transmitted via A delta or via C fibers. It meets the criteria of a screening test by being easy to administer, taking little time, being comfortable in handling, and inexpensive while providing high specificity for relevant information