A3 receptor agonist modulates IL-1ß hippocampus levels in a rat model of neuropathic pain

Introduction: Considering the lack of specific treatments for neuropathic pain, this study aimed to evaluate the effect of a single dose of adenosine A3 receptor IB-MECA on inflammatory and neurotrophic parameters in rats subjected to a neuropathic pain model. Methods: 64 adult male Wistar rats were used. Neuropathic pain was induced by chronic constriction injury (CCI) of the sciatic nerve and the treatment consisted of a 0.5 µmol/kg dose of IB-MECA, a selective A3 adenosine receptor agonist, dissolved in 3% DMSO; vehicle groups received DMSO 3% in saline solution, and morphine groups received 5 mg/kg. Cerebral cortex and hippocampus IL-1ß, BDNF, and NGF levels were determined by Enzyme-Linked Immunosorbent assay. Results: The main outcome was that a single dose of IB-MECA was able to modulate the IL-1ß hippocampal levels in neuropathic pain induced by CCI and the DMSO increased IL-1ß and NGF hippocampal levels in sham-operated rats. However, we did not observe this effect when the DMSO was used as vehicle for IB-MECA, indicating that IB-MECA was able to prevent the effect of DMSO. Conclusions: Considering that the IL-1ß role in neuropathic pain and the contributions of the hippocampus are well explored, our result corroborates the relationship between the A3 receptor and the process of chronic pain maintenance.

Transcranial direct current stimulation did not revert the increased central and peripheral NGF levels induced by neuropathic pain in rats / Tratamento com estimulação transcraniana por corrente contínua não reverteu o aumento de NGF induzido por modelo de dor neuropática em ratos

ABSTRACT BACKGROUND AND OBJECTIVES: The expression of nerve growth factor (NGF) in the large-size neurons may represent a key role in the neuronal synaptic plasticity and re-organization of neuronal function after a nerve injury. Transcranial direct current stimulation (tDCS) is a non-invasive method of cerebral stimulation and represents a promising tool to pain management since it promotes neuroplasticity in the central system, and it can be combined with other interventions. The aim was to investigate the effects of tDCS in the NGF levels in central and peripheral nervous system structures of rats submitted to a neuropathic pain (NP) model. METHODS: The chronic constriction injury (CCI) of sciatic nerve was used for the induction of NP. For sham surgery, the sciatic nerve was exposed, but without any ligation. The control group did not undergo surgical procedure. After the establishment of NP, treated groups were subjected to tDCS treatment 0.5 mA/20min/day/8 days. NGF levels in cerebral cortex, spinal cord and sciatic nerve were determined by sandwich-ELISA at 48 hours and 7 days after the end of treatment. RESULTS: The CCI model increased NGF levels in all three structures analyzed at long-lasting time, evidencing the importance of this neurotrophin in neuropathic pain condition. On the other hand, there was no tDCS effect in the central and peripheral NGF levels discarding the participation of this neurotrophin in the analgesic tDCS effect. CONCLUSION: tDCS modulation effects of nociceptive pathways seem not to be linked to the NGF signaling in this chronic pain model.

RESUMO JUSTIFICATIVA E OBJETIVOS: A expressão do fator de crescimento neural (NGF) em neurônios de diâmetro largo pode representar um papel importante na plasticidade sináptica neuronal e na reorganização da função neuronal após lesão neural. A estimulação transcraniana por corrente contínua (ETCC) é um método não invasivo de estimulação cerebral e representa uma ferramenta promissora para o manejo da dor, pois promove neuroplasticidade no sistema central, podendo ser combinada com outras intervenções. O objetivo foi investigar os efeitos da ETCC nos níveis de NGF em estruturas do sistema nervoso central e periférico de ratos submetidos a um modelo de dor neuropática (DN). MÉTODOS: A constrição crônica (CCI) do nervo isquiático foi utilizada para indução do modelo de DN. Na cirurgia sham, o nervo foi exposto, no entanto não houve constrição do nervo. O grupo controle não foi submetido ao procedimento cirúrgico. Após estabelecimento da DN, os grupos tratados foram submetidos a ETCC 0,5 mA/20min/dia/8 dias. Os níveis de NGF no córtex cerebral, medula espinal e nervo isquiático foram mensurados pela técnica de ELISA 48 horas e 7 dias após o final do tratamento. RESULTADOS: O modelo de dor CCI aumentou os níveis de NGF nas três estruturas analisadas, evidenciando a importância desta neurotrofina na dor neuropática. Por outro lado, não houve efeito da ETCC nos níveis de NGF central e periférico, descartando o papel desta neurotrofina no efeito analgésico da ETCC. CONCLUSÃO: Efeitos da ETCC sobre vias nociceptivas não estão diretamente relacionados com a sinalização do NGF neste modelo de dor crônica.

tDCS and exercise improve anxiety-like behavior and locomotion in chronic pain rats via modulation of neurotrophins and inflammatory mediators.

Anxiety disorders cause distress and are commonly found to be comorbid with chronic pain. Both are difficult-to-treat conditions for which alternative treatment options are being pursued. This study aimed to evaluate the effects of transcranial direct current stimulation (tDCS), treadmill exercise, or both, on anxiety-like behavior and associated growth factors and inflammatory markers in the hippocampus and sciatic nerve of rats with neuropathic pain. Male Wistar rats (n = 216) were subjected to sham-surgery or sciatic nerve constriction for pain induction. Fourteen days following neuropathic pain establishment, either bimodal tDCS, treadmill exercise, or a combination of both was used for 20 min a day for 8 consecutive days. The elevated plus-maze test was used to assess anxiety-like behavior and locomotor activity during the early (24 h) or late (7 days) phase after the end of treatment. BDNF, TNF-ɑ, and IL-10 levels in the hippocampus, and BDNF, NGF, and IL-10 levels in the sciatic nerve were assessed 48 h or 7 days after the end of treatment. Rats from the pain groups developed an anxiety-like state. Both tDCS and treadmill exercise provided ethological and neurochemical alterations induced by pain in the early and/or late phase, and a modest synergic effect between tDCS and exercise was observed. These results indicate that non-invasive neuromodulatory approaches can attenuate both anxiety-like status and locomotor activity and alter the biochemical profile in the hippocampus and sciatic nerve of rats with neuropathic pain and that combined interventions may be considered as a treatment option.

Antinociceptive and neurochemical effects of a single dose of IB-MECA in chronic pain rat models.

This study aimed to evaluate the effect of a single administration of IB-MECA, an A3 adenosine receptor agonist, upon the nociceptive response and central biomarkers of rats submitted to chronic pain models. A total of 136 adult male Wistar rats were divided into two protocols: (1) chronic inflammatory pain (CIP) using complete Freund's adjuvant and (2) neuropathic pain (NP) by chronic constriction injury of the sciatic nerve. Thermal and mechanical hyperalgesia was measured using von Frey (VF), Randal-Selitto (RS), and hot plate (HP) tests. Rats were treated with a single dose of IB-MECA (0.5 µmol/kg i.p.), a vehicle (dimethyl sulfoxide-DMSO), or positive control (morphine, 5 mg/kg i.p.). Interleukin 1ß (IL-1ß), brain-derived neurotrophic factor (BDNF), and nerve growth factor (NGF) levels were measured in the brainstem and spinal cord using enzyme-linked immunosorbent assay (ELISA). The establishment of the chronic pain (CIP or NP) model was observed 14 days after induction by a decreased nociceptive threshold in all three tests (GEE, P < 0.05). The antinociceptive effect of a single dose of IB-MECA was observed in both chronic pain models, but this was more effective in NP model. There was an increase in IL-1ß levels promoted by CIP. NP model promoted increase in the brainstem BDNF levels, which was reversed by IB-MECA.

Single exercise stress reduces central neurotrophins levels and adenosine A1 and A2 receptors expression, but does not revert opioid-induced hyperalgesia in rats.

BACKGROUND: This study assessed the effects of an acute stress model upon the long-term hyperalgesia induced by repeated morphine administration in neonatal rats. We also evaluated neurotrophins and cytokines levels; expressions of adenosine and acetylcholine receptors, and acetylcholinesterase enzyme at the spinal cord. MATERIAL AND METHODS: Male Wistar rats were subjected to morphine or saline administration from P8 to P14. Thermal hyperalgesia and mechanical hyperesthesia were assessed using the hot plate (HP) and von Frey (vF) tests, respectively, at postnatal day P30 and P60. After baseline measurements, rats were subjected to a single exercise session, as an acute stress model, at P30 or P60. We measured the levels of BDNF and NGF, interleukin-6, and IL-10 in the cerebral cortex and the brainstem; and the expression levels of adenosine and muscarinic receptors, as well as acetylcholinesterase (AChE) enzyme at the spinal cord. RESULTS: A stress exercise session was not able to revert the morphine-induced hyperalgesia. The morphine and exercise association in rats induced a decrease in the neurotrophins brainstem levels, and A1 , A2A , A2B receptors expression in the spinal cord, and an increase in the IL-6 cortical levels. The exercise reduced M2 receptors expression in the spinal cord of naive rats, while morphine prevented this effect. CONCLUSIONS: Single session of exercise does not revert hyperalgesia induced by morphine in rats; however, morphine plus exercise modulate neurotrophins, IL-6 central levels, and expression of adenosine receptors.

Transcranial direct current stimulation combined with exercise modulates the inflammatory profile and hyperalgesic response in rats subjected to a neuropathic pain model: Long-term effects.

BACKGROUND: Behavioral alterations, like mechanical and thermal hyperalgesia, and modulation of biomarkers in the peripheral and central nervous systems (CNS) are markers of chronic pain. Transcranial direct current stimulation (tDCS) with exercise is a promising therapy for pain due to its neuromodulatory capacity. OBJECTIVE: To assess the individual effects of tDCS, exercise, and the two combined on the nociceptive response and BDNF, IL-1ß, and IL-4 levels in the CNS structures of rats in a chronic pain model. METHODS: For 8 consecutive days after the establishment of chronic neuropathic pain by inducing a constriction injury to the sciatic nerve (CCI), the rats received tDCS, exercise, or both treatments combined (20 min/day). The hyperalgesic response was assessed by von Frey and hot plate tests at baseline, 7, and 14 days after CCI surgery and immediately, 24 h, and 7 days after the end of treatment. The BDNF, IL-1ß, and IL-4 levels were assessed in the cerebral cortex, brainstem, and spinal cord by enzyme-linked immunosorbent assay at 48 h and 7 days after the end of treatment. RESULTS: The CCI model triggered marked mechanical and thermal hyperalgesia. However, bimodal tDCS, aerobic exercise, and the two combined relieved nociceptive behavior for up to 7 days following treatment completion. CONCLUSIONS: Bimodal tDCS, aerobic exercise, or both treatments combined promoted analgesic effects for neuropathic pain. Such effects were reflected by cytokine modulation throughout the spinal cord-brainstem-cerebral cortex axis.

Transcranial direct current stimulation (tDCS) and trigeminal pain: A preclinical study.

OBJECTIVE: Our objective was to evaluate the Transcranial direct current stimulation (tDCS) effect on facial allodynia induced by chronic constriction of the infraorbital nerve (CCI-ION) and on the brainstem levels of TNF-α, NGF, IL-10, and serum LDH in rats. METHODS: Rats were exposed to the CCI-ION model. Facial allodynia was assessed by von Frey filaments test at baseline, 3, 7, 10, and 14 days postsurgery and 24 hr and 7 days after the bimodal tDCS sessions for 20 min/day/8 days. RESULTS: Chronic constriction of the infraorbital nerve induced a significant decrease in the mechanical threshold 14 days after surgery. This effect was reversed by tDCS treatment, with the mechanical threshold returning to basal levels at 24 hr after the end of the treatment and it persisted for 7 days after the end of the treatment. tDCS also decreased LDH serum levels compared to those in the control group. There was an interaction between pain and treatment with respect to brainstem levels of NGF, TNF-α, and IL-10. CONCLUSION: Chronic constriction of the infraorbital nerve model was effective in establishing trigeminal neuropathic pain on 14 days after surgery, and tDCS reduced allodynia and LDH serum levels and promoted alterations in NGF, TNF-α, and IL-10 brainstem levels. Thus, we suggest that tDCS may be a potential therapy in the trigeminal pain treatment.

Active post-operative phoned search for late infections of surgical site and thromboembolic events in the late postoperative period of plastic surgeries in a day hospital in the municipality of Porto Alegre

Introduction: Elective and plastic surgical procedures are normally considered safer than emergency surgeries, although they cause concern to health services. The aim of this study was to analyze the active phoned search as a screening instrument for the diagnosis of surgical site infection (SSI) and thromboembolic events (TEs) in the late postoperative care of plastic surgeries in a private day hospital in the city of Porto Alegre. Methods: Quantitative, descriptive, retrospective, cross-sectional study. Data was collected from a database provided by phoned active search of sign and symptoms for epidemiological monitoring by the control infection service of a day-hospital, from July 2015 to February 2017. Results: A total of 3.595 patients were effective contacted in the indicated period. Among these patients, 77.6% received guidance on TEs. Moreover, 0.4% and 0.2% of patients reported signs and symptoms of SSI and TE, respectively. Associated procedures caused 50.0% of SSIs and 87.5% of TEs. Phoned search increased in 0.2% the number of reported cases of both adverse events in the overall sample. Conclusion: SSI and TE are worrying events for health institutions, since they can put patient safety at risk. Therefore, the data obtained in this study were used as a basis to qualify phoned search as an effective screening instrument for SSI and TE and provided support for the development of more consistent phoned search mechanisms for monitoring these postoperative events. (AU)

Anti-inflammatory effect of an adhesive resin containing indomethacin-loaded nanocapsules.

OBJECTIVE: To analyze the anti-inflammatory and analgesic effects of an adhesive resin containing indomethacin-loaded nanocapsules in rat model. DESIGN: Adhesive resin disks with or without indomethacin-loaded nanocapsules were subcutaneously implanted into right hind paw of rats. A week after surgical procedure, 2% formalin solution was intradermally injected into plantar surface of paw. Nociceptive and inflammatory responses were evaluated by formalin test. Paw edema by pletismometer and mechanical hyperalgesia by von Frey test were performed on day 2, day 4, day 6, day 8, day 10 and day 12 after surgery. IL-6, IL-10, and lactate dehydrogenase (LDH) serum levels were determined by ELISA-sandwich test. RESULTS: Group containing indomethacin-loaded nanocapsules (NC) presented lower edema in the right hind paw at 24h after formalin injection than those of the control group (CT) (P<0.01). NC group showed decrease in the nociceptive response in phase I (neurogenic pain) compared to CT group (NC - 66.86±22.83s X CT - 130.17±35.83s, P<0.001). NC group presented supporting higher intensity of stimulus on days 8 and 12 (24h and 72h after formalin injection) (P<0.01 and P<0.02 respectively). The IL-6 serum level was also significantly higher in the NC group than CT group (p<0.001). CONCLUSIONS: These results indicate that an adhesive resin containing indomethacin-loaded nanocapsules has anti-inflammatory and nociceptive activities in a chemical model of acute inflammation. The present investigation confirms an adhesive resin with drug-loaded nanocapsules may be useful for improving therapeutic effect for adhesives to be used in deep cavities.

Melatonin Alters the Mechanical and Thermal Hyperalgesia Induced by Orofacial Pain Model in Rats.

Melatonin is a neuroendocrine hormone that presents a wide range of physiological functions including regulating circadian rhythms and sleep, enhancing immune function, sleep improvement, and antioxidant effects. In addition, melatonin has received special attention in pain treatment since it is effective and presents few adverse effects. In this study, we evaluated the effect of acute dose of melatonin upon hyperalgesia induced by complete Freund's adjuvant in a chronic orofacial pain model in Sprague-Dawley rats. Nociceptive behavior was assessed by facial Von Frey and the hot plate tests at baseline and thereafter 30, 60, and 120 min, 24 h, and 7 days after melatonin treatment. We demonstrated that acute melatonin administration alters mechanical and thermal hyperalgesia induced by an orofacial pain model (TMD), highlighting that the melatonin effect upon mechanical hyperalgesia remained until 7 days after its administration. Besides, we observed specific tissue profiles of neuroimmunomodulators linked to pain conditions and/or melatonin effect (brain-derived neurotrophic factor, nerve growth factor, and interleukins 6 and 10) in the brainstem levels, and its effects were state-dependent of the baseline of these animals.

Long-Lasting Effect of Transcranial Direct Current Stimulation in the Reversal of Hyperalgesia and Cytokine Alterations Induced by the Neuropathic Pain Model.

BACKGROUND: Neuropathic pain (NP) is caused by an insult or dysfunction in the peripheral or central nervous system (CNS), the main symptoms being mechanical allodynia and hyperalgesia. NP often shows insufficient response to classic analgesics and its management remains a challenge. Transcranial direct current stimulation (tDCS) is a non-invasive method of cerebral stimulation and represents a promising resource for pain management. OBJECTIVE/HYPOTHESIS: We investigated the effects of tDCS on the nociceptive response and on IL-1ß, IL-10, and TNF-α levels in CNS structures of rats with NP. METHODS: After induction of NP by chronic constriction injury (CCI) of the sciatic nerve, the rats received 20 min of bicephalic tDCS for 8 days. Hyperalgesia was assessed by the hot plate and von Frey tests and evaluated at baseline, 7 days, and 14 days after CCI surgery, and also immediately, 24 hours, and 7 days following tDCS treatment. The levels of IL-1ß, IL-10 and TNF-α in the cortex, spinal cord, and brainstem were determined by ELISA at 48 hours and 7 days post-tDCS. RESULTS: The CCI model provoked thermal and mechanical hyperalgesia until at least 30 days post-CCI; however, bicephalic tDCS relieved the nociceptive behavior for up to 7 days after treatment completion. CONCLUSIONS: Bicephalic tDCS is effective to promote antinociceptive behavior in neuropathic pain, which can be reflected by a spinal neuroimmunomodulation linked to pro- and anti-inflammatory cytokine levels observed in the long-term.

Transcranial direct current stimulation (tDCS) reverts behavioral alterations and brainstem BDNF level increase induced by neuropathic pain model: Long-lasting effect.

INTRODUCTION: Neuropathic pain (NP) is a chronic pain modality that usually results of damage in the somatosensory system. NP often shows insufficient response to classic analgesics and remains a challenge to medical treatment. The transcranial direct current stimulation (tDCS) is a non-invasive technique, which induces neuroplastic changes in central nervous system of animals and humans. The brain derived neurotrophic factor plays an important role in synaptic plasticity process. Behavior changes such as decreased locomotor and exploratory activities and anxiety disorders are common comorbidities associated with NP. OBJECTIVE: Evaluate the effect of tDCS treatment on locomotor and exploratory activities, and anxiety-like behavior, and peripheral and central BDNF levels in rats submitted to neuropathic pain model. METHODS: Rats were randomly divided: Ss, SsS, SsT, NP, NpS, and NpT. The neuropathic pain model was induced by partial sciatic nerve compression at 14 days after surgery; the tDCS treatment was initiated. The animals of treated groups were subjected to a 20 minute session of tDCS, for eight days. The Open Field and Elevated Pluz Maze tests were applied 24 h (phase I) and 7 days (phase II) after the end of tDCS treatment. The serum, spinal cord, brainstem and cerebral cortex BDNF levels were determined 48 h (phase I) and 8 days (phase II) after tDCS treatment by ELISA. RESULTS: The chronic constriction injury (CCI) induces decrease in locomotor and exploratory activities, increases in the behavior-like anxiety, and increases in the brainstem BDNF levels, the last, in phase II (one-way ANOVA/SNK, P<0.05 for all). The tDCS treatment already reverted all these effects induced by CCI (one-way ANOVA/SNK, P<0.05 for all). Furthermore, the tDCS treatment decreased serum and cerebral cortex BDNF levels and it increased these levels in the spinal cord in phase II (one-way ANOVA/SNK, P<0.05). CONCLUSION: tDCS reverts behavioral alterations associated to neuropathic pain, indicating possible analgesic and anxiolytic tDCS effects. tDCS treatment induces changes in the BDNF levels in different regions of the central nervous system (CNS), and this effect can be attributed to different cellular signaling activations.

Obesity and chronic stress are able to desynchronize the temporal pattern of serum levels of leptin and triglycerides.

Disruption of the circadian system can lead to metabolic dysfunction as a response to environmental alterations. This study assessed the effects of the association between obesity and chronic stress on the temporal pattern of serum levels of adipogenic markers and corticosterone in rats. We evaluated weekly weight, delta weight, Lee index, and weight fractions of adipose tissue (mesenteric, MAT; subcutaneous, SAT; and pericardial, PAT) to control for hypercaloric diet-induced obesity model efficacy. Wistar rats were divided into four groups: standard chow (C), hypercaloric diet (HD), stress plus standard chow (S), and stress plus hypercaloric diet (SHD), and analyzed at three time points: ZT0, ZT12, and ZT18. Stressed animals were subjected to chronic stress for 1h per day, 5 days per week, during 80 days. The chronic exposure to a hypercaloric diet was an effective model for the induction of obesity and metabolic syndrome, increasing delta weight, Lee index, weight fractions of adipose tissue, and triglycerides and leptin levels. We confirmed the presence of a temporal pattern in the release of triglycerides, corticosterone, leptin, and adiponectin in naïve animals. Chronic stress reduced delta weight, MAT weight, and levels of triglycerides, total cholesterol, and leptin. There were interactions between chronic stress and obesity and serum total cholesterol levels, between time points and obesity and adiponectin and corticosterone levels, and between time points and chronic stress and serum leptin levels. In conclusion, both parameters were able to desynchronize the temporal pattern of leptin and triglyceride release, which could contribute to the development of metabolic diseases such as obesity and metabolic syndrome.

Interrelação entre síndrome metabólica, estresse crônico e ritmos circadianos de marcadores adipogênicos: uma revisão / Interrelation between metabolic syndrome, chronic stress and circadian rhythms of adipogenic markers: a review

Alterações de ritmos circadianos são relacionadas ao desenvolvimento de transtornos metabólicos como obesidade e síndrome metabólica. Além disto, a disponibilidade e o consumo de alimentos altamente palatáveis ricos em gordura e a exposição a situações estressantes podem contribuir na incidência e na severidade destas doenças crônicas, provocando modificações no balanço energético, alterações no metabolismo de lipídeos e adipogênese. Nesta revisão, abordaremos os aspectos cronobiológicos que podem ser influenciados pela exposição a estresse crônico e a obesidade, além dos mecanismos que contribuem para o crescimento de doenças metabólicas (AU)

Alterations in circadian rhythms are associated with the development of metabolic disorders, such as obesity and metabolic syndrome. Moreover, the availability and consumption of highly palatable foods rich in fat and the exposure to stressful situations may contribute to the incidence and severity of these chronic diseases, leading to changes in energy balance, alterations in lipid metabolism and adipogenesis. This review aimed to discuss the chronobiological aspects that can be influenced by the response to chronic stress and obesity, as well as the mechanisms that contribute to the development of metabolic diseases (AU)

Fentanyl administration in infant rats produces long-term behavioral responses.

Considering the importance of studies in animal models that are focused on systems involved in pain mechanisms, this investigation aimed to evaluate the effects of pharmacological treatments on the behavioral responses of younger animals. To this end, we evaluated the effect of an acute dose of fentanyl (FEN) or S(+)-ketamine (KET) at postnatal day 14 (P14) upon behavioral responses in the short- (P14), medium- (P30) and long-term (P60) using the open field (OF), elevated plus-maze (EPM) and formalin tests (FT) and tail-flick latency. Fourteen-day-old male Wistar rats were divided into three groups: control (CT), fentanyl (FEN) and S(+)ketamine (KET) groups for statistical analysis, it was performed two-way ANOVA followed by Bonferroni. We found that, regardless of the test performed (OF or EPM), between-group differences occurred over time in all behaviors analyzed, including in the second phase of FT. In addition, EPM showed significant differences in behavioral responses related to acute administration (at P14) of fentanyl or S(+)-ketamine, in behaviors such as number of entries in open and closed arms, time spent in open and closed arms, and number of head-dipping. In relation to nociceptive response, the FEN group exhibited a decrease in the first phase of FT. These results indicate that unique administration of fentanyl or S(+)ketamine in an early period of life (P14) can promote changes in behavioral responses. In addition, our findings highlight the importance of extending the investigation of the effect of drug administration in young rats into adulthood.